A small pimple on the foot that is particularly painful when touched lightly may be caused by boils, tendon sheath cysts that become infected, corns and other diseases. 1. Boils: If they occur around hair follicles and have obvious local redness, swelling, heat and pain, it is considered that they may be caused by boils. Diabetes, anemia, malnutrition, etc. will increase the risk of this disease, and can be treated with iodine tincture, mupirocin and other drugs. 2. Infection of tendon sheath cysts: If it occurs near the joints, it may be caused by tendon sheath cysts, which are clearly demarcated from the surrounding tissues and painful when accompanied by infections, and can be treated by pinprick and extrusion. 3. Chicken eye: preferred in adult women, is due to long-term friction and pressure on the foot caused by keratin layer hyperplasia, the patient will have a localized elevated bumps, light pressure will be painful, can be taken to surgical excision. There may be other reasons why a small lump on the foot hurts when lightly touched, so patients are advised to go to the hospital in time for a clear diagnosis and treatment under the guidance of the doctor.