When an insect bites it leaves a black scar on my skin.why this happens ? what should i do?

P.I.H. : Postinflammatory hyperpigmentation (PIH) is 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. Time usually helps fade the PIH. There are lasers that can also help. Hope this helps.