Thats part of raising kittens. You have to be stern with him, when he does this and convey that it hurts. He doesn't know any better yet and doesn't know how to express himself.
My old cat also bit, when she didn't wanted to be touched anymore or when I touched her at a body part where she wasn't comfortable being touched. It's what they do with other cats too. But she learned to be gentle about it and often licked over it right after as a kind of apology like "Stop this, I'm sorry, I don't mean to hurt you.
When they are little they can't controll the strength of their bite and also the impact of their claws. But they understand and learn if you show what hurts you.
My cat like to be petted... but not to be touched... it's a cat thing
This dumpster Goblin doesn't like to be pet but is perfectly fine being held and pet. Plus he climbed on me for the first time a week ago
Over-stimulation. Stop earlier when you see the signs. (I've adopted a problematic cat that would bite too hard). https://imfelinefab.com/behavior/2019/4/18/the-right-way-to-pet-your-cats
