If it is cut bad enough to make him limp, then there is a serious risk of infection. Remember, kitty paws in the litter box! At least call your vet, if not make a visit. You could try covering it, but good luck getting any sort of bandage to stay on kitty! (ever seen a cat with a piece of tape stuck to its paw? They will go nuts trying to get it off!)
I like most cats better than I like most people. I'll try to be nicer if you try to be smarter.