My daughter (12 months) has been teething for the past 2 weeks - and in the past 3-4 days, she's gotten her FOUR top-front teeth.
As we've been going through this teething process - she bit me SEVERAL times while nursing. ... Each time, I yelped, "OUCH!" (Mainly because that was my reaction when she did it!) ... I'd look at her and firmly say, "No biting!" ... Then put her down for a second.
She would look at me with a shocked look on her face, then promptly burst into tears ... I'd wait a second, then scoop her up, cuddle her, and try and resume nursing. (Sometimes she'd nurse just fine - other times, she'd bite me again, and we'd repeat the above scenario.)
However, in the course of going through that - she actually broke the skin on my nipples twice - causing me to bleed a little bit - and also form scabs on my nipples.