Funny mark on breast

I'm in a bit of trouble, I have an unexplained mark on my boob. I'm pretty sure it's just a bruise from work but my boyfriend thinks it's a love bite. Are there differences between a bruise and a love bite? Also I recently got my nipples pierced (a month ago), I don't know if it has any link. Anybody have advice? Anybody ever had unexplained marks turn up like this?