Nkunku barely stays fit; he cannot play for two months, IMO.
Nkunku have not always been an injury prone player, they're are just some types of injuries that when a player have them staying fit for a longer period becomes a problem just like it was with Reece James and Ousmane Dembele too, these use to be players that get a lot of tackles and almost never got injured, but since that just one injury it became a problem to play for a month with having a reoccurrence or another similar problem.
I guess Nkunku might have to play with avoiding contact a lot at least for the foreseeable future to prevent any other form of set back, should he stay fit though, I'm curious to see how Chelsea plan to integrate him into the team without having to alter how and the position Cole Palmer would occupy on the pitch.