If that rear-ender did not cause your airbag to go off, the forces were not even close to a concussive force. The whiplash may have traumatized your neck and cause muscle tightening that can be problematic.

When looking for neck therapy, it is a crap shoot. No one speciality can provide the proper treatment. As I have said, What worked for me was myofacial release to reduce the neck muscle spasms then gentle traction and mobilization to help the cervical vertebra settle into proper position. Follow this with disciplined behaviors to not stress the neck during sleep.

I've had more struggles in the morning from bad sleep and sleep posture than from activities in the day.