Did I have a missed TBI 18 years ago?

20 years ago, when I was 16 year old boy, I was "king hit" by an adult on the street and he broke my jaw in two places. I'm now starting wonder if I have a brain injury as I experience symptoms of fatigue, irritability, concentration issues and impulsivity. I've recently obtained the hospital records and I was observed for a concussion but nothing was noted. All the treatment was about the broken jaw. There was never any follow up about my brain. It was not until I went back to the location the assault occurred 2 years ago that I suddenly experienced overwhelming flashbacks about the incident (that I previously couldn't remember a lot of) and its been on my mind since. My GP recently asked me if I had hit my head on pavement and I didn't, but only because someone screamed "run" and I managed to catch myself on a bin just before I did. He said its unlikely I have a BMI if I didn't hit me head. And because I was punched on the front of the face, the jaw would have took the impact. But I feel like he's being dismissive. And that perhaps its more common for hospitals to miss TBI 20 years ago?

I'm not sure where to go next. Is it even worth a neuro-psych or something? Perhaps the incident was just too long ago... I felt dismissed by the GP. Are there neuro-affirming practitioners out there that are worth consults?