Any questionable skin lesions should be seen by a physician - whether its your family physician, urologist or a dermatologist.
Possible causes can include benign skin disease (i.e. birthmark), a fungal infection, folliculitis (infection of the hair follicles), as well as STDs such as genital warts or herpes. Treatment of the skin condition would depend on the cause.
Your family physician should be able to refer you to a urologist or dermatologist.
A list of urologists can be found here:
http://www.urologyhealth.org/find_urologist/
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.