Yesterday in the middle of the day I noticed my neck was stiff and very sore. Especially the very back of the neck, from the base of my skull all the way down to my shoulder. It's very hard to touch my chin to my chest, I can feel my muscle straining and it feels painful. It also hurts to look all the way up. I don't notice any other symptoms other than a slight headache and my neck is hot to the touch. (but no fever)

I've tried putting a warm cloth on it, I've tried slowly stretching it and also have taken ibuprofen. No improvement.

I cannot think of any reason why this is happening. I didn't wake up with it, I just noticed it randomly during the middle of the day yesterday. What could be causing this? Should I be concerned? How long should this last?

Also, what can I do to help ease the pain or make it less stiff?