There are exercises you can do, look them up under "neck pain from working on the computer;" some stretches and stuff. Not that this comes from only working on the computer, but if you are right-handed and mouse with your right hand, it's a suspect.
Hi there and welcome to med help. Ya know, I was in a car accident about 16 years ago. I've had this same exact thing. Terrible.
I assume you are seeing a doctor --- and if not, it is best to see one. Maybe muscle relaxers would be prescribed or an around the clock nosteriodal antiinflamatory such as ibuprofen. This helps with pain relief and swelling. You might try a chiropractor or physical therapy as well. There are stretches that I'd try to do. They do help overall
What I found to be of most benefit was massage. I didn't do the fru fru full body massage but went to a massotherapist that worked only on my neck and shoulder. It wasn't a feel good at the time kind of thng but he worked to release what was tight internally in that area. It helped so much. You can maybe get a referrel from your doctor for someone that gives this type of massage in your area.
Take that ibuprofen and get lots of rest. I also find when I'm tired or stressed, I get an acute flare up from the chronic situation. good luck