The main reasons for this are as follows: 1. It may be a symptom of the forthcoming menstruation, the hormone secretion disorder in women’s bodies before the menstruation will stimulate the nipples and cause the nipples to swell and hurt. 2. The company’s main business is to provide a wide range of products and services to the market. If the pain is obvious, it is recommended to go to the hospital for a specific examination in time.