I had this from sleeping on my grandmas couch. If it was as bad as mine, your neck is sideways. It's really hard to keep it straight, but to go to the opposite side is painful, and pretty much impossible. A stiff neck heals itself. Advil will help short term, even though I wouldn't recommend taking it. One thing to try is lay on the floor, stay in perfect posture, and don't move for 15 minutes, then get up take a warm shower, then right after do it for 10 more minutes, get up and you should feel somewhat better. It was probably from sleeping, and you need to sleep, sit, and maintain a perfect posture while doing everything for it to heel as fast as you may like.