Hi ,May be it's because of your attaing wrong posture and sleeping pattern or may be a history of fall
You can apply hot pack on painful site about 10 to 15 min twice a day for 1 week .
Next Steps
If your pain still persist I advised for xray n rush to physiotherapy/orthopaedic department for proper diagnosis to start the appropriate treatment
Health Tips
Owing safety measures
don't lie on painfull site, stop overusing you painfull arm as well as give some rest.