Paris St-Germain say Brazil forward Neymar has “sprained his ankle” and suffered “some ligament damage”.
The 31-year-old picked up the injury in the second half of his side’s win against Lille at the weekend and was carried off on a stretcher.
PSG added Neymar would “undergo further tests at the start of next week”.
The French champions will try to overturn a 1-0 deficit at Bayern Munich in the second leg of their last-16 Champions League tie on 8 March.
Neymar has scored 18 goals and registered 17 assists for PSG this season, with two goals and three assists coming in the Champions League.