A hard lump on the inner side of the thigh may be caused by boils, dermatofibromas and epidermal cysts, which usually do not go away on their own, and it is recommended to take medication, surgery and physical therapy to improve the condition. 1. Boil: A hard lump on the inner side of the thigh may be caused by a boil. If the lesion is not pus-filled, antibiotics such as mupirocin and fusidic acid can be applied as prescribed by the doctor to help inhibit bacteria and reduce inflammation. If the lesions recur, oral antibiotics, including amoxicillin and cefuroxime, should be prescribed to promote recovery. Surgical incision can be performed if necessary. 2. Dermatofibroma, epidermoid cysts: Dermatofibroma, epidermoid cysts are usually treated with surgery; in addition, laser treatment, cryotherapy and other ways also help to improve the dermatofibroma and epidermoid cysts, and it is recommended that the patient according to their own situation, cooperate with the doctor for standardized treatment. There are many reasons for a hard lump on the inner side of the thigh root, so it is recommended that the patient should consult a doctor for examination, clarify the cause of the disease, and cooperate with the doctor for standardized treatment.