It means they are bonding/bonded with you. Bonded bunnies do this to groom or play with one another. It is literally like a love bite. As long as it is a little nibble and not a hard bite but I’d trust you’d know the difference as bites can be painful.That’s exactly what he does! He nudges my hand with his nose, sniffs around and then nibbles once but I do feel it every time. Is he trying to be friendly or is be unhappy with something?