There is a possibility of sudden muscle spasm following panic attack leading to strain in the muscles around sternum.. At some particular angle, stress may rise over that area this causing pain..
Next Steps
I will suggest you to start with hot fomentation, take analgesic with muscle relaxant tablet for few days, apply local analgesic ointment over the site of pain 3-4 times daily
Health Tips
Avoid heavy work, avoid forward bending, avoid weight lifting exercises..