Hello,
This can be due to hyperpigmentation. Without treatment, this usually takes about 6 months to resolve and for the skin color to go back to its normal color. Topical treatments with acids and chemical peels can be effective but can take a while for the skin to totally revert to its normal color. Microdermabrasion can also be done, but this might require several sessions. Skin resurfacing using lasers is also an option.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Several years ago, I made the mistake of getting my eyebrows waxed while using Retin-A. Big mistake!! But its not a mistake that will cause scarring. Our facial skin renews itself alot quicker than skin elsewhere on the body. Keep the burned area clean of infection, use neosporin or similar, and then use pure aloe vera after the skin has healed. It'll take a several long weeks to see the brown marks lighten up and disappear. Lesson learned, no more waxing, instead try threading while using topical medications. Good luck!