it seems that you are suffering from trapezitis. trapezius is a musle connecting skull, neck, shoulder and upper back. it may go in to rigid spasm in conditions like cold
atmosphere, continuous working in neck down position
you may relief from mild hot water fomentation like hot water bag and application of analgesic
you have not mentioned the chest pain
side left or right. if these pains are not subsided by above means then consult your doctor.
wishing you best of health goodbye ...