For starters, diseases that cause warts are different from those that cause melanoma. Most warts are caused by viruses and can be passed to others, including gential warts passed on by sex.
Melanoma is one of 3 types of skin cancer along with basal cell carcinoma and squamous cell carcinoma(which my cat died of last year). The others spread slowly and get larger and look more like either a scaly patch that starts to enlarge and perhaps bleed or a sore that won't heal and slowly gets larger. Melanoma however can stay very small and looks like a mole. It may not get bigger but go deeper and invade a blood vessel when it sends out more cells that set up home in whatever organ then want and then they grow until they push the normal tissue out of the way and slowly destroy the normal cells until you die. Melanoma can even affect the iris of the eye(the colored part). It is so deadly because by the time you have symptoms, it's usually because it has spread.
If you are having problems, see a doctor. No, painful urinating is not part of melanoma but it could be you picked up genital warts. And if you have, the chances are you may have picked up another STD from the same person. People who have these problems and pass them along often don't care about partners and can give them something else as well. STD's can be treated with medication and genital warts can be treated as well.
See a doctor.
