Rabbits are pretty skittish, normally. It’s worse if they’re not socialized, and they bite when threatened.
Have you ever seen a rabbit’s mouth?
"Like any other rodent bite, a rabbit bite could result in bruising; blue or yellow discoloration of the skin is normal. Some swelling can also occur. If you have been bitten and have not had a tetanus shot within the past five years, contact a doctor. If the wound looks like it is becoming infected or if the rabbit that bit you was not a household pet, you should also contact the doctor."