Small hard bumps under the soles of the feet are generally referred to as corns, calluses, or plantar warts, which can be treated by laser, surgery, or liquid nitrogen. 1. corns: corns are caused by excessive friction and prolonged standing, which can be eliminated by laser cauterization, or in severe cases, by corns removal surgery. 2. callus: occurs in the palm and metatarsal pressure and friction, yellow or waxy yellow thickened keratinous plaques, commonly known as callus, generally no obvious discomfort, do not need treatment. 3. metatarsal warts: patients infected with human papilloma virus, may occur on the soles of the feet rash and then formed metatarsal warts, after the friction and extrusion of the warts caused by the rupture of small blood vessels, the formation of small black spots. The warts are usually treated with laser or liquid nitrogen, which causes the warts to necrose and then fall off. There are other ways of treating small hard bumps on the soles of the feet, any of which should be done under the advice of a doctor. If any significant discomfort occurs, you should immediately visit a specialized hospital for effective treatment.