Doug Morgan, the tour manager, said: "Nichol was examined again this morning and we were advised by the medics that he would not be available for the next two games. We had no alternative but to send him home."
The tour has already taken a heavy toll as last weekend Craig Chalmers, Rowen Shepherd and Ian Smith all returned home and it is expected that Jamie Mayer, the young Watsonian centre, will also be out of the tour after injuring his ankle on Wednesday.
Nick Greenstock, the Wasps centre who made his international debut on the recent tour of Argentina, has been named as Will Greenwood's replacement for England's one-off Test against Australia in Sydney on 12 July.
Greenwood was ruled out after being concussed playing for the Lions against Free State Cheetahs on Tuesday.
England have been forced to make two further changes, with the Bath winger Jon Sleightholme coming in for his team-mate Adedayo Adebayo, who has a groin injury, and Leicester's Richard Cockerill takes the place of the Gloucester hooker Phil Greening.
Nottingham have failed to sign the former England winger Rory Underwood. Although Underwood held talks with Barrie Corless, Nottingham's director of rugby, he now seems likely to link up with Bedford. Corless has instead secured the services of Tom Reynolds, a 26-year-old farmer, who was unable to commit himself to full-time training with Leicester.
London Scottish have signed a New Zealand Barbarian and four players who were in the top flight of the national league last season. Stand-off Jamie Cameron, 27, played seven Super 12 matches for Wellington Hurricanes in 1996, when he was top points scorer in New Zealand. With a Scottish grandfather, he is hoping to catch the eye of the Scotland selectors.
Cameron's half-back partner will be Steven Cook, 23, who has joined the club from Orrell, and London Scottish have also signed three players from Harlequins: the No 8 or second row forward Mick Watson, flanker Simon Owen and centre Rhodri Davies.
Australia have dropped a plan to play the All Blacks at Twickenham later this year, but they could play Scotland at Murrayfield instead.
The Wallabies are negotiating with the Scottish Rugby Union for an international to follow their November tour of Argentina. John O'Neill, the Australian Rugby Union chief executive, said the Scotland match would go ahead if the SRU tripled its offer from pounds 100,000 to pounds 300,000.
O'Neill claimed South Africa were initially offered the larger amount for a similar one-off match and the Australians were seeking the same fee.