It does matter that he’s 3 months old, this is the time when he’s becoming sexually mature. Bunny courtship is a lot about nipping. Other signs of courtship are that he follows you around, run in circles around you/your feet, pee-spraying on you and places were you often are and grunting. If he starts doing any of those things + the biting, then you can interpret it as courtship, he “thinks” you are a girl-bunny and he “wants” to start a family with you. It’s not that he actually thinks or wants, it’s hormonally driven compulsive behavior so he’s not really choosing to do it.
In case this isn’t hormonal:
Try to squel instead, it’s more like the sound a hurt bun would do.
Nibbling as you describe it is not aggressive. Rabbits often communicate with their teeths and mouths. Could it be that he wants you to pet him? Or that he wants a treat/more food? Or is he trying to get to know you and everything about you by exploring you with his teeth?
You should of course try and not encourage his biting. You shouldn’t punish him, that only scares a rabbit, but you can remove him from you if you think he’s doing it for attention, just make sure you do it very quickly, almost as the bite starts (in like split seconds), so he makes the connection between biting and being removed.