Bleeding after fingering?

My boyfriend and I had a great time today because we were out of condoms. We just masturbated with our hands/fingers. When it was his turn, we stopped for a moment to change positions. When I saw that his fingers were red, I asked him, "Why is there blood?" We both thought I had gotten my period (which could have been, since I was actually supposed to get it tomorrow), so we stopped for a moment and got tissues. After I went to the bathroom and at least 10 minutes had passed, not a drop of blood came out, so it wasn't my period. I didn't have any pads/tampons on all day, so nothing came out. Why did that happen? My boyfriend also had short fingernails, or none at all, which could have hurt me. It doesn't hurt, but like I said, I haven't bled for hours. It was like a nosebleed.