My son would use his teeth when he was sleepily nursing. I remember them getting so sore when he had a cold and wanted to comfort feed like that. Like what pp said make him re latch deeper. When my son bit on purpose I would firmly say no and take it away for a little. At that age he cried when I told him no and it was so sad but the biting was worse lol.

Is he biting you or just nursing with teeth? My son went through stages of both. For biting, I’d pull him off, say “owch, it hurts when you bite me” and then we’d be done for a few minutes. It took a day and he never bit me intentionally again.

If he’s nursing with teeth, that’s a little trickier. You’ll have to retrain his latch. My son would get lazy with his latch if he were sleepy. Sometimes I could fix it myself without making him unlatch, just my pushing around my boob. But many times we had to unlatch and make sure he got a better deeper latch. You may want to consider working with a lactation consultant if the problem persists.

When baby girl started doing that I stopped the nursing said ouch! no! As I pointed my finger & that seemed to help. Lol I stopped nursing at 8 teeth but because I was pregnant and wanted a break before the new one arrives and I'd have to start all over.