The winger sustained the injury during Dons’ last outing, the 1-1 draw with Accrington Stanley.
Boss Neal Ardley said: “Chris played really well when he came on but he got a nasty challenge and his ankle came up like a balloon.
“We had our fingers crossed but the scan showed a fracture rather than ligament damage.
“There is not much we can do about impact injuries, we’ll just have to take this one on the chin.”
This is an untimely blow for the club who have not won in their last three attempts.
Sheffield United could have leading scorer Leon Clarke back for their home game against Nottingham Forest.