There is a hard lump under the chin and it hurts because of hair follicle infection, body surface swelling, lymph node enlargement, etc., as follows: First, hair follicle infection: common in young people or people with high oil secretion, if the pain is not too strong, you can apply iodophor or Bactrim for anti-inflammatory, if it is more serious, you need to go to the dermatology department for disposal; Second, body surface swelling: such as sebaceous cyst, you need to go to the hospital’s Third, swollen lymph nodes: there are many reasons for swollen lymph nodes, such as bacterial infection, viral infection, tuberculosis infection, autoimmune system disease, blood system disease, and even malignant tumor. Sometimes, puncture biopsy or excisional biopsy of lymph nodes is required to clarify the nature of the disease.