Hummels went off at halftime in Saturday's match. The club said Sunday that the Germany defender will miss Tuesday's Champions League match against Galatasaray and next weekend's Bundesliga game against Borussia Moenchengladbach.
Those games are followed by a two-week Bundesliga break for internationals, with Germany playing a European Championship qualifier against Gibraltar and a friendly in Spain.
The German has long been linked with a switch to the Premier League.
Hummels' injury adds to Dortmund's woes in what has been its worst start to a Bundesliga season. Saturday's defeat was its seventh in the opening 10 games and left it in the relegation playoff place.