Plantar warts are caused by the human papilloma virus. This is contagious and can spread. The chances of spreading increases if you pick at it.
Treatment options include freezing it with either liquid nitrogen or a device called the histofreezer. You can also cauterize it which effectively vapourises the tissue.
The former option involves cutting the overlying skin down before treatment. The cold tip is then applied for 1 minute, allowed to thaw then repeated. Repeat treatments (since 1 treatment is usually not enough) are done every 2 weeks (very important!), during which the wart shrinks as the overlying skin peels off.
The latter options is done under local anesthesia and is sometimes a faster way of treatment but leaves you with and open would and a longer recovery time. This may also have to be repeated.
I have found treatment of warts to usually be difficult, which sometimes requires multiple visits. But they do resolve eventually.
