I'd probably do a lot of cardio and workout legs a few times a week until the hand heals up.
If it's blistering up, you don't want to fuck around like Chiro said. The gym is a breeding ground for germs, and while I never wipe shit down or anything a blister is like bending over and telling Vince Goodrum to have at it with no spit. You really, really don't want to put yourself into that situation.