Treat him as though YOU are his mother. Mother cats play with their babies but when the babies start biting or hurting, mom cuffs them lightly on the side of the head and they walk away. A few times of you QUITING playing, he'll get the idea. Also, I clip my 2 cat's nails EVERY Sunday morning. I have one that sleeps thru the process he's so used to it -- and they're almost 4 yrs old. Cutting those nails back would help a lot.