Need detail history how pain has started,onset duration ,any aggravating factor , any relief after taking medication n all

If you are doing some heavy workout like using heavy weights at gym, it maybe because of that. Or there might me muscle cramps, for which you need to be adequately hydrated. Take plenty of water 2.5-3.5L per day. In case the pain worsens , or if there is any additional complaints, you can consult whenever you like to. Thank you for asking. Hope I was able to curb your doubt. Stay healthy. Stay home. :)

Probably its a muscle pain if it is associated with movement of left arm...