A painful bump on the bottom of the foot is commonly caused by either a callus or a wart. Calluses are thickening of the skin due to excess pressure, friction, or shear to certain areas of the feet. Warts are skin growths caused by a common virus (human papillomavirus or HPV) in the superficial skin of the foot. The virus is contagious and can be spread to others with casual skin contact. Make an appointment with Dr. Cowans today. He will determine the cause of the painful bumps and develop a treatment plan tailored to your needs and wants.