Tmi, but advice, please. Strange blood?

So, a few days ago, I was hanging out with this guy and we were a little drunk and messing around. He fingered me then went down on me, sorry to be so graphic but it's important to the story. We ended up havjng sex, which started with a condom but ended without one because of reasons that are irrelevant but he pulled out. The power went out and I was scared to go to the bathroom alone after because I'd never been there before so he went with me and he found out he had blood all over his mouth and I wiped and I was bleeding. I checked my glow and it was the 15th day of my cycle, not that that's relevant other than to point out that it wasn't my period. Why could I have been bleeding??