Foot warts are small growths about the size of a pencil eraser, but some can grow bigger, states WebMD. They are usually hard, and they may grow in clusters. In some cases, warts may have blood vessels that appear as small, black dots.
Also known as plantar warts, foot warts are grainy growths that appear on the bottom of the foot and tend to be common in children, according to WebMD. They are noncancerous skin growths caused by the human papillomavirus. Most foot warts are not a source of concern and may not require treatment. However, they can cause pain and discomfort, notes Mayo Clinic.