When you feel like your neck pain happens when you wake up and you think that you slept wrong, you should contact your chiropractor the same day to make an appointment for an evaluation and treatment. The earlier you do so, the least amount of time it will take to go away.
If you can’t have an appointment on the same day, you can apply heat (with a heat pad) on the affected area and leave it for 12-15 min at a time 2-3 times per day. Remember when you apply a heat pad, have a layer of a towel or two under it to avoid overheating. You can also use some over the counter pain relieving cream like Arnika, Tiger balm or Biofreeze, but REMEMBER THAT IF YOU USE THE CREAM CONTAINING MENTHOL OR CAMPHOR, YOU CANNOT USE THE HEAT PAD RIGHT ON TOP OF IT OR RIGHT AFTER IT because it could irritate/burn the skin under it. So, use those two things at least an hour away from each other. Taking hot showers/bath/hot tub can also help temporarily.