Labia turning black

The skin flap beneath my clitoris been itching these past few days and when i checked, the color is turning black(it used to be reddish pink in color)only at the tip.. before this happened i washed them with dirty water before they started to itch(was at a dirty public restroom and had no other choice) i am not sexually active, though i had my first oral encounter just a week before and he rubbed his around my area. Should i get this checked? I am 25.