Bleeding Nipple!!!

HELP!!so the other day me and SO were laying in bed and my nipple started bleeding. only the left. he said not to worry it was probably from rough sex or the cat scratching me. Fast forward. today I got home and took off my clothes like typical and all of the sudden I look down and dark almost black blood started coming out of my nipple. SO came over and squeezed it (to make sure it wasnt just a "scratch" even though i told him it wasnt) nd a good bit came out. it's still bleeding now