The Germany international took a blow to the same foot in a friendly game with Fortuna Dusseldorf on Tuesday morning.
He has sprained and jarred his ankle, but the club's doctor Markus Braun, while confirming "an approximately two-week rehabilitation phase" for the 25-year-old, says that the ligaments he tore while playing for Germany against England last November are "fully healed".
With Hummels back in their defence, Dortmund picked up their first win in five last weekend, beating Eintracht Braunschweig 2-1 to move up to third in the Bundesliga.
Hummels will now miss their games against Werder Bremen and Eintracht Frankfurt in the Bundesliga, as well as against Frankfurt in the DFB-Pokal next week.
He could also miss the trip to Hamburg on February 22, while coach Jurgen Klopp will be hoping to have him back for the Champions League last-16 tie at Zenit St Petersburg three days later.