The warm water and compresses will help the muscles relax, and the pills should help if there is any pain and inflammation.
For the most part, if it is not sever pain, you may have just slept wrong, and the soreness should go away in a day or two. If not, you need to see a doctor ASAP.
I had neck problems for three years, and they suck. If you grind you teeth at night this can also make your neck sore, might want to look into a mouth guard.