My face got black due to acne or some other blood problem what to do for getting my original colour of my face?

See dermatologist: What you describe is post-inflammatory hyperpigmentation (pih), a frequently encountered problem particularly in darker pigmented individuals including african americans or asians. Pih occurs as a result of inflammation to skin. Acne is common inflammatory diseases that results in pih, particularly if one picks at their lesions. See a dermatologist to get appropriate treatment.