The Colombian striker injured himself earlier today as the Blues prepared for tomorrow night's Champions League Group G match against Dynamo Kiev at Stamford Bridge.
"It's an important injury," Mourinho told reporters. "Not as important as the ones he has previously had, but one that will keep him out for a couple of weeks."
Falcao, 29, is at Chelsea on a season-long loan from Monaco. He has made just one Premier League start for the West London side this term and netted only once in 11 total appearances.