Hello and welcome to HCM.
It will better if you mention your age and any significant medical condition of present.
Aching pain in left arm can be due to heart related conditions or it can simply pain associated with problems in muscles,joints,nerves.
If I were your treating doctor,I recommend,
-Advice blood pressure measurement,blood glucose,
blood lipids and ECG.If anything found positive,further management will depend on it.
-
Analgesic like
acetaminophen for 3-5 days.Avoid taking NSAIDs like
ibuprofen till heart conditions are ruled out.
-Warm compression locally and around joints..Also local application of
diclofenac gel can be done.
If the above tests are normal and the pain persists or worsens beyond ,you will need to visit orthopaedician.
Hope this information helps.
Thanks and regards.