As you have told ,, seems like you just like a black hyperpigmented mark over your forehead....
Since it is a dark scar, i would advice that you use some kind of a lightening agent like kojic acid
and vitamin c
combination over the scar,,this is a simple, harmless lightening agent which can be used for as long the blackish pigmentation is there.. Also ,try not to touch the area too much ...use proper sunscreen (spf>26) before going out in the sun so that the lesion doesn't darken any further....and take a diet rich in vitamin C and antioxidants
like Citrus fruits and lots of salads
Hope it helps
Dr Geetika Paul