Sore nipples

Today I woke round 5am and one of my nipples was so sore, but it sort of went away and the last 3hours both nipples are so to touch. It not the whole breast that hurt it just the nipples. I just finish ouvlating. I don't think I'm pregnant.

I never get sore nipples before. I just wondering if it do woth ovulating why their are sore