Quietly, almost inaudibly, he tells how he was forced to work as a goatherd for an Arab family, how he lost a goat one day and was made to hold a piece of burning charcoal in his hand as punishment, how they broke his teeth and how, eventually, he ran away and sought refuge with another Arab family who treated him well and sent him to school.
Chimir was found there five months ago by a committee of Dinka chiefs formed to try to trace the thousands of children abducted during 16 years of civil war in southern Sudan. He has now been brought to Khartoum along with several others whose cases are expected to take a long time to solve.
Good news has just come for a little boy called Garang, thought to be about five years old. He was abducted when he was about two, but the committee says it has now managed to track down his father, through other Dinkas who know the family. But Chimir's chances of going home in the near future are slim at best: he does not even remember his parents' names.
Chimir and Garang are among countless children whose lives have been torn apart by Sudan's civil war. As many as 2 million people are thought to have died, either directly or as a result of famine caused by the war, while more than 4 million people have been displaced - half of them children. Many now live in dismal slums on the outskirts of Khartoum.
Hundreds of thousands of children - most of them southerners - end up on the streets of the capital. "The main factor is that their families are too poor to feed and clothe them," said Hashim Zakaria, director of a local aid organisation, the Sudanese Popular Committee for Relief and Rehabilitation. "Some of them have also been forced on to the streets because they have lost their parents."
In the early 1990s, the government swept many street children into camps outside Khartoum where they were forced to speak Arabic and were given Muslim names. Some were sent to fight in the south. The camps have now been disbanded, but the problem of street children has only got worse.
Africa's largest country has been devastated by civil war between the Muslim north and the mainly Christian and animist south. The government is thought to spend $1m a day on the conflict - money that is desperately needed elsewhere.
Government hospitals in Khartoum had to stop performing all major surgery last week because the capital's central medical laboratory had run out of chemicals to test blood for HIV and hepatitis. "If I have an emergency now, I'll have to give them untested blood," said the director of emergencies at one Khartoum hospital. "It's a big dilemma - while trying to
treat them I may also be making them ill with something else." Medical treatment that used to be free now comes at a cost that few Sudanese can afford.
Doctors say health services have deteriorated dramatically as they have received less and less public funding. "In rural areas, staff at government clinics are paid irregularly, if at all," said a doctor working with the French organisation, Medecins sans Frontieres. "Essential drugs are routinely not available."
The education system has suffered similarly. "There's a shortage of government schools and even in those schools some fees are required," said Mr Zakaria. "We did a survey in Khartoum six months ago that found that 40 per cent of children of school age weren't going to school because their parents couldn't afford the fees and the food they would eat there."
Not surprisingly, most Sudanese are now desperate for change. "Every day, people are dying at the front," one young man said. "What a waste. If the war ended this country could be transformed."
A glimmer of hope has come from an unexpected quarter: the power struggle within Sudan's Islamist leadership. President Omar el-Bashir has ditched his eminence grise, Hassan al-Turabi, the parliamentary speaker, dissolving the legislature and calling a state of emergency. Mr Turabi is deeply unpopular, and there are now hopes that Mr Bashir will push ahead with efforts to achieve political reconciliation in the north and peace in the south.
But it is an enormously complex conflict, of which the last 16 years of bloodshed are only the latest bout. Many in the international community are concerned that recent American moves to provide food aid to the main southern rebel group, the SPLA - if they go ahead - will only prolong the war. There is also a risk that the power struggle between Mr Bashir and Mr Turabi could turn violent, dragging Sudan into yet more bloodshed.
The Sudanese people, already impoverished, can ill afford further conflict. Many people, especially the displaced, are expected to go hungry in the year 2000.
"The main problem we face now is that although there are food surpluses in some areas, the poor can't afford to eat properly," said Mr Zakaria. "And when you have poverty you have children forced on to the streets. We expect the number of street children to increase next year."
As long as the war continues, there will also be little hope of any real solution to the plight of the thousands of children, like Chimir, who have been abducted and abused as part of the conflict.