such type of pain is very common these days due to the life style of todays requiring more often sitting in front of computer it may be because of the spasm of the trapezius muscle or in your terms the muscle of your neck and shoulder
Next Steps
you can have some hot fomentation of the neck and shoulder 15 min twice aa day and then stretch your neck muscles side ways opposite side and also stretch your shoulder muscles fromall the sides i hope thats surely is going to relieve your problem
Health Tips
try to avoid bad posture of sitting and take frequent intervals between your job