Thanks for writing your query.
It will be helpful if you give more information about your job profile.
After reading your post, it seems that your pain is musculoskeletal in origin.
You can take painkiller like Ibuprofen
twice daily after meals along with a muscle relaxant
and an antacid
You can apply locally pain relieving oil after doing hot fomentation.
I would also suggest that you should get an X-Ray of your Left Shoulder(AP and Lateral view) done and consult an Orthopedician for clinical examination.
Avoid lifting heavy weights from your left hand.
I hope this is helpful to you.