Biting during nursing

My teething six month old has started biting down on my nipples while nursing. It's so painful that I almost wanted to sling him off of me. I don't know what to do. He thinks it's amusing to see me screaming from the pain of his bites. I don't want to stop breastfeeding, but I'm terrified to see how awful it will feel once his teeth pop through. Any advice will be welcomed with open arms!