Hours later?

Shelby • Mama to Sydney 💕 👧🏼 I love being a girl mama!
Hi everyone! 
So my boyfriend and I had sex around 6:30 this morning. It was a little rough but nothing crazy. Now, at 1:00 this afternoon, I went to the bathroom and there's some light blood. Isn't isn't brown, old blood, it's pink. Any idea why this could be happening hours after the fact? 
Thanks!