Symptoms suggest spasm..probably due to abnormal posture..
You can try:
1. Hot water compression thrice daily for 1 week.
2. Light shoulder exercises.
3. Give rest to affected shoulder.
4. Medications like Myoril, Etova MR, Enzomac and Neurokind LC will help.
Next Steps
If pain does not relieve by 4-5 days then you can visit Orthopaedic Surgeon for clinical evaluation and X-Rays.
Health Tips
Do not worry .