I personally would have waited 10-15 minutes before letting him nurse again. If he bites again, can you push your finger into the side of his mouth between the gums where there are no teeth? That's what I do, she finds it funny when her face is shoved into my body. Then I say NO, don't bite, it hurts, unlatch her and the session is over.
It hasn't happened often, maybe 4-5 times. She got the message I think.