My vagina is turning black?!?

So I discovered a bump on my labia- upon investigating (making sure it wasn't something serious) I noticed that my skin around my clitoris ( at the top of my inner folds) had darkened.... Like a dark grey. Now I don't know if this is something I should be concerned about or if it's something that happens over time????  I've never heard of a vagina changing color...It's upsetting because it gives my vagina a kind of decaying flesh look... Like ew. Before I go to the doctor and embarrass my self even more I just need to ask!