Its nothing but the pain/spasm of the trapezius muscle of cervical spine which generally occurs due to overwork/manual exertions /long neck bending /long travelling/driving /computer work /cold exposure.
Next Steps
Go to a physiotherapist.. Ultrasonic therapy +IFT +Heating therapy +some strengthening exercises as well as stretching will be helpful for sure. It will help in breaking the pain-spasm cycle .
Health Tips
At home.. Rest +hot water fomentation +pain killer gel +no long sitting /travelling /driving /computer work /table work /studies +no cold exposure +no manual exertions /weight lifting +correct posture.