Detail history and discussion is needed to suggest treatment, consult with me directly through Practo. Take care

Could be frozen shoulder or pain could be coming from the cervical spine. Get Blood sugar test done. Consult me on line for specific treatment options

Looking at the history given by you and assuming that you are unable to seek medical care due to corona virus lock down I am giving my opinion. Left arm pain and restricted movements especially if you have diabetes is likely to be Frozen shoulder or Adhesive capsulitis. It is a self limiting disease but very painful during initial stage. If you don't have any history of diabetes , hypertension, renal disease or allergies then you can try Tab voveran d 50 mg twice a day after meals and you can also do hot fomentation and take rest.

Make sure there is no cardiac problem. Pain may be from neck or shoulder . Physio might help. At cure t situation do hot or ice fomentation and shoulder exercises. Consult orthopaedic dr near you

We need certain other details Is there a neck pain..? From where to where is the pain-  is it from shoulder to hands and fingers or from elbow to hands or is it just localised to arm How are the movements -is it painful /restricted.? Is there tingling numbness Is there any history of injury..? Is there pain in any other region apart from this..? Is there a pain during rest This would help us in diagnosing and treatment

Take any analgesic muscle relasaant IND analgesic ointment for five days consult me online thru practo