Sore nipple discharge may be caused by normal physiological phenomenon, mastitis, breast hyperplasia and so on. 1. Physiological phenomenon: increased levels of estrogen may lead to nipple pain discharge, mainly occurs during puberty and pregnancy, this is a normal physiological phenomenon. 2. Mastitis: When breastfeeding women’s milk stagnation is accompanied by bacterial infections, forming breast abscesses, pus discharge with milk may appear in the nipple. 3. Mastoid hyperplasia: sore nipple discharge is mainly plasma or plasma blood, which is a common symptom of mastoid hyperplasia, because of follicular hyperplasia accompanied by dilatation of the ducts, resulting in the formation of fluid in the lumen of the ducts. Symptoms of nipple pain discharge may also be other causes, such as breast cancer, etc., please go to the regular hospital in time, active diagnosis and treatment, so as not to delay the condition.