Sore Nipples Now look burnt :/

I am currently on the marvelon pill, have had unprotected sex however have endometriosis & distorted tubes (point as I'm unlikely pregnant) on Sunday my boobs ached above the nipples when I took my top off for a shower I noticed my nipples we're hard & very sore. Once in the shower the heat running down my chest felt like it was stinging or burning them (very odd) I woke up with dark marks (look like burns) on the tip of my nipples has any idea what that could be?