It could be a nerve
In view of the history of CAD in your case, any pain on the left side of chest will naturally draw attention to heart and cause anxiety
. As you have mentioned that you have recently had a heart check up and nothing abnormal was detected, i`m of the opinion that you need not worry.
Since you have not mentioned about any other symptoms like cough
, breathlessness etc, the pain could be because of some minor nerve getting irritated or because of some muscle fibre strain. You may take some pain killer and apply some local heat and analgesic
However, if pain persists for a long time you may consult your cardiiologist once again.