A hard lump on the leg may be folliculitis, nodular itchy rash, erythema nodosum and other diseases, and you should consult a doctor in time to clarify the cause. 1. Folliculitis: If the hard bumps on the legs are grown around the hair follicles, it may be the marks caused by folliculitis prolonged, usually without special treatment. 2. Nodular itchy rash: insect bites, gastrointestinal dysfunction and other factors leading to chronic inflammatory skin diseases, patients will have relatively large skin bumps, preferably in the calf extensor, reddish-brown or grayish-brown, sometimes accompanied by itching. 3. Erythema nodosum: an inflammatory disease that occurs in the intervals of subcutaneous fat lobules, there will be erythema nodosum of both calves with significant tenderness, which is also manifested as a hard lump on the leg. There may be other causes of the above situation, it is recommended to go to the hospital in time, clear diagnosis, symptomatic treatment.