Sex and blood?

So-- 
I was having sex with someone and when they came they looked at me and asked if I was on my period. Apparently, I was bleeding. But it was only a little bit. It's not my time and it stopped Right away? 
Is it possible he tore me up a little bit? 
The night before we had sex and I was perfectly fine.
 I mean I felt a slight uncomfortable soreness but it wasn't that powerful. So...I don't know. I was a bit sore all day today.