A hard lump under the chin that is painful when pressed may be related to diseases such as lymphadenitis and skin boils. 1. Lymphadenitis: Lymph nodes are normal immune tissues distributed in various parts of the body, among which the jaw area is the main distribution area of lymph nodes. Normally, the size of lymph nodes is less than 5 millimeters. When the area where they are located shows symptoms of infection it leads to localized inflammation, enlargement and pain in the lymph nodes. 2. Skin boil: It is an acute infection that occurs deep in the hair follicle, and before abscess formation, it is mainly manifested as a small subcutaneous mass, and there may be a certain degree of pressure and pain. Due to the uncertainty of the time of onset and the course of the disease, it is recommended that the patient go to the hospital for a clear diagnosis under the guidance of the doctor and follow the doctor’s instructions.