Majewski suffered the injury early on in the 4-1 Championship defeat to Millwall at the City Ground last Saturday.
However, it is still not clear whether the Polish midfielder will have to undergo an operation.
Reds boss Sean O'Driscoll said: "The medical people are going to see how it settles down and decide whether he needs surgery or not. Nobody wants an operation and if we can get a good prognosis that he will be okay then he won't have one.
"But we are hedging our bets. We don't want to get two months down the line and then find that he needs an operation.
"That is something the consultant, surgeon and physios will look at and make a decision on but it is going be months now rather than weeks."