Acne scars are scars 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 using TCA on your own as it may cause irritant contact dermatitis or chemical burns.
My sincere advice would be to consult a dermatologist.
I hope that helps. Please do keep me posted on how you are doing or if you have any additional queries. Kind regards.