What Causes Nipple Pain In Male?

i went to work this morning and im a mover and like 3 hours into the move my nipples started hurting and feel like there on fire like a really really bad sunburn would make you feel but its my nipples so its worse it was hot and i was really sweaty but kept a shirt on the whole time why do they feel like they do and what can i do there is no change in color or anything im a guy 29yrs