I've had stabbing pain in my sternum that hurts in
See a doctor if it is severe...
If the pain is severe, then I don't think it's good to wait for long time.
Are you able to perform your daily activities without trouble?
Are you able to climb flight of stairs?
Do you have breathing difficulties, palpitation, cough or fever?
Based on your current description of symptoms, it may be due hyperacidity / GERD. Until you see a doctor, I would suggest starting a proton pump inhibitor / antacid available over the counter along with probiotic agents. These might help you with hyperacidity and GERD symptoms.
Hope this helps. Let me know if you need clarifications.