Small amount of bleeding, is this common?

Hello, I was just curious to know if this is a common thing or not. My boyfriend was fingering me, and I started bleeding. I wasn't gushing out blood, just a very small amount came out. We stopped when it happened. He was rough, so I'm thinking he might have just caused some damage. 

Could this cause any permanent damage, and is there a more specific reason for this? I know for a fact I'm not pregnant  nor have I ever had actual sexual intercourse, but me and my boyfriend have been doing other things for quite some time now.

Thank you for any information :-|