Dent in forehead 5 months after assault resulting in concussion (Photo)

It's probably due to  tissue atrophy secondary to the trauma.  A filler should be helpful.  Find an experience filler injector and obtain a consultation.

Presuming that the Head CT scan did not reveal any fracture of the frontal bone this dent is most likely a result of loss of fat and soft tissue from the blunt trauma. This type of soft tissue injury is generally easy to correct using fillers such as restylane to fill in the hole and even out the skin. It sounds like you are still recovering from your injuries but once your ready a consultation with a facial specialist experienced in fillers would be a good next step. Fillers are a quick ,easy in office procedure and should work great in correcting this depression. 

Your traumatic forehead dent could be from soft tissue atrophy or from an indentation in the bone. Knowing that distinction is important as the treatment would different for a soft vs hard tissue contour restoration. (fat graft vs bone cement) That diagnosis could be determined by a 3D Skull CT scan.