What Is The Black Mole In My Inner Cheek?

Hi, Im 29 yrs old women. I was brushing my teeth earlier & just found out that I have a black mole on my right cheeks which was never there. Well not that I know of. It's painless! Im very concern, What should I do? How can u get this especially when my inner mouth is never exposed to the sun. Pls help! THX!