Hi Welcome to Healthcare Magic Forum From your description, there are two possibilities that come to my mind.. Either it is a post inflammatory /trauma pigmented scar or it is a Fixed drug eruption If you remember having developed any injury of any lesion on the same area in the past , then chances of post inflammatory or post trauma scar are more.. However, a Fixed drug eruption is a type of allergic reaction to a medicine. Fresh lesions are well defined, round or oval patches of redness and swelling of the skin, sometimes surmounted by a blister. This then fades to a purplish or brown colour. The number of drugs capable of causing fixed eruptions is large. Most are due to the following: Paracetamol /phenacetin and other pain killers,Tetracycline antibiotics; doxycycline , minocycline ,Sulphonamide antibiotics, Acetylsalicylic acid/aspirin Make sure that you are not regularly on any of these medications. In either case, you need to apply a lightening agent containing Kojic acid and vitamin C combination to the affected area twice a day daily.. use sunscreen before any sun exposure if it is on a sun exposed area. Take oral vitamin C supplementation for early recovery Hope it helps Wishing you speedy recovery Dr Geetika Paul