Fingering?

Last night my boyfriend came over and he fingered me really well, but also really hard and it actually felt like sex. Well I ended up bleeding from there, like alot. I started crying cause I was so embarrassed but he was okay with it and cleaned up for me and comforted me. Well anyways it's still on my mind as for why I'm bleeding. It isn't the first time this happened. But all I could think of was that he cut me with his fingernail in there, because I'm not on my period, it ended like 5 days ago. Did anyone have this happen before and have a reason why it could be?