When I strech my back, there's a bubbly feeling below my right rib cage (near center of chest). There is no pain but just a feeling something is there when I strech. When I do a yoga cobra pose, the bubbling sensation or feeling that something is there is more prominent.
reference stock photo of yoga cobra pose:
https://thumbs.dreamstime.com/z/middle-aged-man-doing-cobra-pose-studio-image-36319973.jpg