"Normal" purpose of pain vs. TMS pain...

My brain has been going back into the uh oh, something is structurally wrong place the past day or so.
I know the answer, but I need some validation on this. Bear with me, I think I've talked about this a million times here. About 2 years ago I was in a very minor car accident - we were stopped at light and rear ended. I was in the middle back seat, no seat belt, and was jolted up, his my head on the car ceiling and I banged down on my tailbone area. Hurt like hell, but briefly as far as I recall. Mostly I was totally freaked out - almost shaking, couldn't get back in the car, actually refused to get back in the car and walked the remaining blocks home, and here's the psych part, felt no one believed me (cf childhood junk) . Was worried I'd wake up in pain the next day, but was actually worrying it would cause jaw problems b/c i was in the midst of a bout of TMJ... Didnt know about TMS at the time... So, no back or leg issues until at least six months after the car thing as far as I recall. When the pain got bad this past year, I realized it was the exact pain as the spot that hurt when I landed on it in the car, and everything that's been going on seems to originate from "the spot." Conveniently, I've got a "large herniated disk at L5 S1." Obviously the spot is associated with fear, almost terror from what I recall, not being supported emotionally etc etc so it makes sense that this is going to be a TMS spot for me. I want to understand though the purpose of the pain at the time in the car - was it just my body properly protecting me and doing what it's supposed to do? My brain thinks "car accident, lasting damage shows up later" and not that my body at the time did what it needed to do. I'm not sure my explanation is quite right on that point so any clarification/ thoughts greatly appreciated!
Thanks!