Hi.. Welcome to HEALTHCARE MAGIC.. I have gone through your query and can understand your concerns.. As per your complain dark spots left after skin infection can be due to Post Inflammatory Hyperpigmentation due to excessive accumulation of melanin producing cells known as Melanocytes in the area of infection leading to formation of a dark spot.. It occurs as a part of protectivve phenomena to protect the skin.. As you have applied chuna [slaked lime ] over it it can further burn your skin leading to darkening of spot and inflammation rather than reducing it.. As you have got a double damage to skin leading to a dark pigmented spot you will have to keep patience and take depigmentation treatment as it can take for about 6 months to even an year for the spot to lighter although can take less time also.. You can start washing your face with salicylic acid and glycolic acid containing facewash like Melaglow, AHA glow etc.. You can use retinoid cleanser.. Apply creams containing Kojic acid, glycolic acid, Vitamin E and C, arbuti etc.. Grapeseed extract can also be helpful.. Exfoliate your skin twice a week.. Limit sun exposure and always apply sunscreen lotion.. You can also go for treatments like Microdermabrasion and chemical peel.. Hope this information helps.. Thanks and regards. Dr.Honey Nandwani Arora..