The lesion that you have described sounds like a scar with post inflammatory hyperpigmentation. The treatment for post inflammatory hyperpigmentation includes various skin creams like hydroquinone, azelaic acid, corticosteroids, tretinoin cream and laser treatment. Apply hydroquinone cream on this scar and it should go away in a few days to months. If it still persists then you can go in for laser treatment, Chemical peeling or microdermabrasion. Avoid picking, harsh scrubbing, and abrasive treatments unless prescribed by a dermatologist during this period.
I hope it helps. Take care and please do keep me posted in case you have any additional doubts. Kind regards.