it sounds like you are doing the exact right thing

my Misha sometimes becomes too loving when being fussed and nips/bites at me but I have seen him do the same in a cuddle/groom session with his brother so I think it is affectionate rather than mean.... after all those sharp teeth could draw blood if he wanted to

just keep being firm and the nips/bites may get to the point where he is gentle enough that you don't mind... he has to learn you have no fur!

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