I think he was looking for attention and doesn’t know he bit too hard if you were a bunny, youd have fur and it would have protected your skin.
Bite inhibition is of course important to try and teach a bun. Squealing can vibe effective. Also, if he is seeking attention, you must see to it that he doesn’t get what he wants. Put him back on the floor etc, just so he doesn’t get rewarded for biting. Dont give him food/a treat ause that’s obviously a major reward ? and is likely to teach him that biting the hoom will get him a treat.
It is important to figure out what he wants and then give him the opposite. If a bun bites aggressively, you must try not to back off because getting rid of the human is what the bun is hoping the bite will result in. Your bun doesn’t seem to be an aggression-biter, but the same principle applies.
With some buns you may even need to wear gloves for starters.