It's probably just seat belt injuries and soreness from that trauma, but you may want to call your primary care Doc and see if they want to do a CT scan or abdominal ultrasound, which I had done in the past for a suspected hernia in the aftermath of lifting a girlfriend and feeling pain in my abdomen and groin.  Make sure you tell the radiologist you have a J Pouch.

I agree with CT. While it may be an injury worth following up on, depending  on the duration and severity, it's unlikely to have anything to do with your pouch.

Your pouch should be OK since it is in a well-protected area.  I was thrown from a horse and had a double spinal fracture, was hit by a car in a crosswalk and involved in a rear-end car collision.  None of these accidents had any effect on my j-pouch.