TMI post

So I’m expected to ovulate tomorrow according to a couple apps, me and my husband BD a little while ago and after we finished we went to clean ourselves ( btw my husband kept his underwear on cause it was a heat of the moment type thing ) anyway we’re in the bathroom and as I was peeing I looked at him and there was light brownish blood on his underwear. I wiped myself and saw some light blood on the toilet paper. I’m not bleeding rn anymore but I’m curious as to why I bled. This has never happened before.