Nipple biting

Katie
My son is 7 months old, and he just started this nipple biting thing. The thing is, every time I tell him "no, don't bite " he cries super hard like I just beat him up! It's super sad to see! 
I don't tell it or say it mean, I'm just wondering if he will stop soon. I'm getting afraid to nurse lol. 
He is teething, and he seems to only do it when he is bored at the end of a session. He also just has noticed I have a nipple and looks to be figuring out what it is. 
I will not stick my finger in his mouth, when he bites down, it really hurts.