Scars from Insect Bite Its 15years Ago?

Large dark scars on the legs from insect bites can be improved with Melarase PM topical cream over 4 to 6 months. Raffy Karamanoukian, Los Angeles

From what you describe, the lesions might not be scars at all.  Many people develop firm brownish to purple growths in response to minor trauma such as an insect bite.  These growths are called dermatofibromas.  The lesions are not only raised above the skin but also have a deeper component.  The only truly effective method of treatment is to surgically excise them.  in general the length of a surgical scar is three times the width of the lesion that is being excised.  For some people the trade off isn't worth it.