First bite at school

Last Thursday Nora was bit or is it bitten on her pointer finger at school. Apparently she was more than brave about the situation. I received a phone call from her teacher letting me know. They (the school) is not allowed to tell me who bit Nora but I think I know who did it. Anyway, it really is not that big of a deal. I just know that this more than likely will not be the only time she gets bitten at school... What is the proper way to use bit or bitten? Who knows....
Exhibit A

Exhibit B