Usually friction: running and gym work in rough or loose fabric chafe nipples raw - fixed by tighter shirts, tape, or barrier balm - plus cold and dry skin.
The medical causes: gynecomastia (a tender rubbery disc of gland tissue behind the nipple, driven by hormone shifts, some medications, steroids, marijuana, alcohol - usually benign, worth an exam), infections (red, hot: prompt care), and rarely male breast cancer - the flags are a hard fixed lump, skin dimpling, inversion, or discharge. Sort: both sides after new gym habits - friction; a tender lump behind one nipple - exam; hard lump or discharge - prompt visit.
What to do
Common questions
Why do my nipples hurt? (men)
The everyday causes lead: friction - running and gym work in rough or loose fabric chafe nipples raw ("jogger nipple" is a real, well-known entity, fixed by tighter shirts, tape, or barrier balm); cold and stimulation (nipples erect and get tender); dry skin and dermatitis. The medical causes worth knowing: gynecomastia - actual gland-tissue growth behind the nipple, driven by hormone shifts (puberty, aging), medications (some blood pressure, psychiatric, and prostate drugs), anabolic steroids, marijuana, and alcohol - the signature is a tender, rubbery disc of tissue directly behind the nipple, common and usually benign but worth an exam; infections (red, hot, swollen - prompt care); and, rarely but real: male breast cancer exists - the flags are a hard fixed lump, skin dimpling, nipple inversion or discharge (especially bloody), one-sided persistence. The sorting: both sides tender after new gym habits - friction. A tender lump behind one nipple - gynecomastia question, get it examined. Hard fixed lump, discharge, skin changes - prompt visit. Pymander, a free AI doctor available 24/7 by text, can help you sort which pattern fits.