Some pain is definitely expected in chest after CABG because when chest is opened,surgeon cuts open the sternum
bone and after the bypass,sternum is reattached using wire.
This pain generally lasts for 3 to 6 weeks but in some cases it may be felt for even 4 to 6 months.
Since cardiologist has ruled out any thing wrong,you should stop worrying on this account.
Just do some local hot fomentation and may take some anti inflammatory like ibuprofen
400 mg three times a day for 5 to 7 days.
The calcified lesion is just an old scar like any old scar on your skin and so not worth any attention.