The usual causes of a sore nipple are: nipple allergy, breast hyperplasia, Montgomery’s nodule infection, mastitis, and eczema-like breast cancer. 1. Nipple allergy: usually associated with fabrics, clothing, food and skin care products stimulation, can be seen in the local skin redness or rash symptoms, can also be manifested in the case of nipples with a lump very painful, it is recommended to keep the nipple local skin clean. 2. Breast hyperplasia: the pain is usually closely related to the menstrual cycle, some patients with breast hyperplasia will also have dilated milk ducts, resulting in nipple overflow, which can easily irritate the nipple, and then small bumps appear with pain. 3. Monsignor’s Nodule Infection: It occurs in the large sebaceous glands around the areola, often due to the blockage of the large sebaceous gland ducts or cleaning is not in place, resulting in bumps on the nipple and accompanied by pain. 4. Mastitis: when the inflammation is close to the nipple, it may irritate the nipple, causing painful nipple bumps, which is a local inflammatory reaction. 5. Eczema-like breast cancer: it is a special type of breast cancer, the lesion is mainly confined to the nipple, most patients will have lumps on nipple and pain, and the nipple will have eczema-like changes. From this we can see that if there are lumps on the nipple and pain, it is recommended to go to regular hospitals in time to find out the diagnosis and get treatment as early as possible.