How Do I Get Rid of Hyperpigmentation from Derma Roller?

I got dermarolling for very mild acne scarring with 1.5 mm June last year on my whole face and developed hyperpigmentation in two spots on my cheek where the doc was more rigorous. Same thing had happened earlier when I was rigorous on a small spot on my thigh dermarolling with a 1.5 mm for some stretch marks & that went away on its own (took some time def but I don't remember how much) and I did mention this to the doc! I don't go out in the sun a lot n try to wear at least spf 15 when i do.