As per the information provided by you it is a muscular pain rather than a joint problem.the area between neck and shoulder is mainly covered by trapezius muscle and small scalene neck muscles which get tight and spasm developes easily in these muscles due to overuse.some people also feel headache due to this and some feel pain and numbness in hand till fingers.very common with people in IT and computer related people.
Next Steps
1.start with heating twise a day.with rubber bottle.
2.do stretching of neck muscles.
3.do strengthening exercises.
4.do not keep head in flexion most of the time.
Health Tips
1.Take pillow for sleep with less thickness.
2.increase water intake.