The causes of nipple pain include menstruation, pregnancy, nipple inflammation, trauma and so on. 1. Menstruation: If a woman is in her menstruation period, her nipples may be sore due to the effect of estrogen. 2. Pregnancy: If a woman is pregnant, the effect of estrogen and progesterone will cause her nipples to become sore and remain erect. 3. Nipple inflammation: If the nipple is infected by bacteria, the bacteria will stimulate the nipple, triggering nipple erection, and at the same time stimulate the nerves will lead to pain. 4. Trauma: when the nipple is damaged by external forces, the nipple will be localized blood swelling, so the phenomenon of erection and swelling. At the same time, the physiological situation of friction stimulation, women’s special physiological period may also appear nipple pain still keep holding. It is recommended that patients with breast discomfort should consult a doctor in a timely manner to determine the cause of the problem and standardize the treatment under the guidance of the doctor.