A hard lump on the inside of the toe may be caused by callus, corns and plantar warts. 1. callus: callus is mainly related to the overgrowth of the cuticle of the skin, including friction, pressure and so on. The patient’s skin will appear thickened and rough, mostly in the hands and feet, etc., manifested as a hard bulge, hard to the touch. 2. Corns: Corns may be related to long-term mechanical stimulation of the skin, long-term walking and other factors. Clinical manifestations of the affected area of the skin bulging, thickening, mostly in the toes, palms of the feet and other places. 3. metatarsal warts: metatarsal warts may be caused by HPV, but also may be related to trauma, sweating and other factors, usually manifested as tiny, shiny papules, and gradually grow to the size of a soybean, most commonly seen in the foot. The causes of a hard lump on the inner side of the toe are more, and it is recommended that the patient go to a regular hospital to clarify the cause of the disease.