Nipple pain

My nipples have been hurting. My son is 21 months and hasn't breastfed in a long while, and I'm NOT trying to get pregnant. (Added that because people always say "you're symptom spotting".) Nope, not attributing this to pregnancy whatsoever, but I do seriously need help. It's random. It's a sharp pain. And it's primarily in my left, but definitely in both. Does anybody have any idea what this could be? I originally thought mastitis or something but I definitely haven't had any milk in there for over a year. Thanks for any help ladies.