Crossing my fingers that this is just the most minor of sprains (if there was a sprain at all). Some general info on recovery times for MCL sprains:
A minor, or grade 1, MCL tear can take from a few days to a week and a half to heal sufficiently for you to return to normal activities, including sports.
A grade 2 tear can take from two to four weeks to heal.
A grade 3 tear usually takes from four to eight weeks to heal, unless it is associated with damage to the ACL, in which case the recovery time may be longer.