I copied this from a site on the internet:
Both men and women experience nipple pain. Men commonly experience this pain following injuries, often from sports or accidents. Men can also develop irritated nipples after exercising, due to friction. Men are also at risk for breast mastitis.
Men are at less risk of developing breast cancer, but the American Cancer Society estimates that in 2018, there will be approximately 2,550 new cases of breast cancer in men.
Men with breast cancer may experience the following symptoms in the nipple:
redness
scaly skin
retraction
It is important for men to be screened and maintain a healthful lifestyle, particularly if they have a high risk of developing this cancer. Family history may be a factor.
Treatment
Cold teabags may help to reduce soreness and pain.
Many home remedies have been used to ease sore and painful nipples. These include:
massage
cold teabags
warm compresses
ice
moisturizers
There is no evidence that these remedies are consistently useful, but some may provide relief, depending on the cause of symptoms. In the event of any changes to the nipple, seek proper diagnosis and medical treatment.
If symptoms occur after exercising, a person can apply a topical barrier product designed for athletes to the skin. Do so before the next workout, to reduce friction.
If symptoms follow the use of a new skincare product, including shampoo, stop using the product and see if the symptoms resolve.