They are difficult to treat without scarring, but left alone, they generally clear spontaneously after a few years. Warts are caused by a virus infection. Many products can be used in attempting to remove warts. This does not slough-off like normal skin cells. These are common warts, but are located around the fingernails and may grow under the fingernail.
Periungual warts are difficult to treat.
By scratching, this individual has spread the virus in a line, causing a line of warts to develop. This linear type spread of warts or other conditions is called the Koebner phenomenon.