A hard bump on the inside of the toe may be caused by callus, corns, plantar warts and other diseases. 1. Callus: mainly manifested as the appearance of hard bumps on the skin, yellow or waxy yellow. The cause of the disease is mainly related to the keratin hyperplasia caused by long-term mechanical stimulation. 2. Corns: yellow or yellowish keratinous growths will appear locally, with smooth surface, the size of a soybean, mostly found on the inner side of the toes, the middle of the front of the foot and other areas. The cause of the disease may be related to the foot by long-term friction, pressure and other factors. 3. metatarsal warts: patients will appear local pimples, with the development of time to form a rough plaque, the surface can be seen black spots, surrounded by thickened keratin, common in the toes, palm and plantar part. The etiology is mainly related to human papillomavirus infection. There are more reasons for a hard lump on the inner side of the toe, so it is recommended to go to a regular hospital for examination and clarification of the cause of the disease.