What Causes The Formation Of Air Bubble At Intercostal Area Of Sternum?

I am 48 years old and am a cardiology nurse. I had a stess test 18 months ago for some atypical pains that I was having at my 4th intercostal rib area just left of my sternum. Stress test was okay except fo r some high blood pressure. 180-90 s was the highest. I had coffee before the test... should not of had stimulants I know. Now starting 5 days ago after eating a vegetable/beef soup with lots of cabbage, corn, carrots, peas and tomatoes in it I have been constantly getting a bubble at my left 34d intercostal area to the right of my sternum. I beltch and it is relieved for a while.... What do you think? YYYY@YYYY