I hope you stretch and warm up your neck and shoulders very well before working out, the shoulder/neck area is easily injured, pull your neck to the right then left then front then back each time holding for at least 20 seconds, then warm up by doing side to side/front to
Back and circular movements. At least 10 times each. After I started doing that I never felt pain in my neck again.
Now on topic, I pulled/injured my lower neck upper shoulders from over working and it take a month or so to fully heal, daily massages will help a lot. And if you can get a steroid shot in the painful area it will go away the next day. Something like decadron. Talk
To your doctor about it, you will still need to rest it for a week or so though.