Nipple pain after menstruation is considered to be mastitis, breast hyperplasia and breast cancer and other diseases, but also may be physiological pain, the specific circumstances should be confirmed in the medical examination in the doctor. 1. Mastitis: Inflammation of the breast tissue infected by microorganisms. It is mostly characterized by swelling and pain. When the skin appears red and swollen, a hard knot appears in a part of the breast, and the nipple feels painful after menstruation. 2. Mammary hyperplasia: due to the change of estrogen in the body, it causes the enlargement and disorganization of breast cells, accompanied by the phenomenon of extensive breast pain, and nipple pain after menstruation. 3. Breast cancer: If the patient suffers from breast cancer, the early symptoms are not obvious. As the condition deteriorates, there will be breast lumps and nipple pain after menstruation. 4. Physiological pain: caused by changes in hormone levels in the body, especially after menstruation, estrogen will increase in the female body, and estrogen will promote the development of breast ducts, which will also lead to nipple pain. Nipple pain after menstruation should also consider other reasons such as trauma, if the cause of pain can not be judged by themselves, or symptoms can not be relieved, you should seek medical attention in time to avoid delay in treatment.