Shoulder injury since October, when will I lose my gains?

I somehow injured my shoulder making a shed in my yard back in October and haven't been to the gym since. Its healing but I feel like I will need 2-4 weeks more rest. I am going on vacation end of march and I have to be in good shape for that.

My question is when you stop going to the gym, when do you start noticing in the mirror. In trying to keep my diet in check but it's hard to stay motivated when not training
*eggs crew*
*raiders crew*