A hard lump grows on the tailbone according to the different causes of treatment are different, common causes are inflammatory cysts, fractures, tumors, etc., the treatment has appropriate rest, medication, surgery and so on. 1. Inflammatory cysts: because of sedentary, tailbone area repeated friction, aseptic inflammation, manifested as sacrococcygeal pain, swelling, you can take oral aceclofenac delayed-release tablets and other non-steroidal anti-inflammatory drugs anti-inflammatory pain. 2. Fracture: there is a history of trauma such as falling on the buttocks and so on, after fracture, the fracture block protrudes to the epidermis, which can be manifested as a hard lump, if the fracture displacement is not obvious, you can take bed rest, if the fracture displacement is obvious, you can have surgical treatment. 3. Tumor: it can be benign tumor or malignant tumor, such as osteochondroma, it is necessary to improve CT, magnetic resonance, pathological biopsy and other examinations to clarify the specific nature of benign tumors, benign tumors can be observed or surgically resected, and malignant tumors can be surgically treated as well as radiotherapy and chemotherapy. The cause of a hard lump on the tailbone is more, it may also be related to sebaceous cysts, lipoma and other diseases, if the symptoms continue to be unrelieved, it is recommended to consult a doctor in time, to clarify the cause of the disease, and to carry out targeted treatment.