Skin lightening on a scar on my stomach that goes towards the lower back. (photos)

So I have this dark mark that has been on my stomach for a long time I can't quite remember when it came. I was not born with it but it could be a birthmark that grew to something as I got older. Now im 21, I'm really self concious when I go to the beach because my stomach is so dark compared to the rest of my body. My lower back is the same color too. Is there a treatment I can do to lighten it completely to match my actual skin color? What is this actually called birthmark/hyperpigmentation?

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