Hi. I'm Concerned I've Been Having A Small Dark Circle

Hi. I'm concerned I've been having a small dark circle on the inside of my left labia i noticed it when I was 17 almost 2yrs ago. I went to the doctors they said it might be a yeast infection they gave me medication for it to put on if it didn't go away they said they would do some analysis I said it went away bc I wasn't comfortable w.a guy Doctor checking and touching me down there. But it still hasn't gone away. as I was doing some research online I've read about pre-cancer which got me scared. But doubt I have that I recently had a baby about two Months ago so I'm sure my obgyn would of said something.. Right? I have no pain no burning sensation nothing. But I know it's not normal to have a small dark spot inside labia for this long. What is it?!?!