Its because of cervical nerve compression. Consult a physiotherapist.
Next Steps
Go to a physiotherapist.. Ultrasonic therapy +IFT +Heating therapy +traction (may require) +some strengthening as well as stretching exercises will be helpful for sure.
Health Tips
At home.. Rest +hot water fomentation +pain killer gel +no long sitting /travelling /driving /computer work /table work +no cold exposure +no manual exertions +no weight lifting +no jerks +no forward bending +correct posture (sit tall).