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The result in your case would depend upon ,how long you have been having the scar, what was the depth of the wound which you had,your complexion , amount of sun exposure etc.
You can start of with using creams like tretinoin
cream ,glycolic creams etc..Use them in the night ,and use a sun blocking cream in the day time.
If this doesn't help then you can also go for lasers ,which work for pigmentation .
Kindly consult a dermatologist
and discuss the prospects of various treatment options including lasers.