Its because of the nerve compression at the cervical region. 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 /forward neck bending /travelling /driving /walking +use cervical collar +avoid cold exposure +no manual exertions +no weight lifting +correct posture (sit tall).