I've had this "thing" under my left ribs for ages. It's not painful, as such, just uncomfortable, like there's summat there. I've had an x-ray, which was clear. This feeling is not always there. When I "break wind", I sometimes get a twinge in this left ribs area. So, is it just a bad case of trapped wind or summat else? Ta Muchly.
If the X-ray was clear I doubt that you've got anything to worry about.
However I bruised my spleen in a fall nearly a decade ago and I still get discomfort under my left ribs, so perhaps there's a connection? (i.e. perhaps you've got a slightly enlarged spleen for some reason?).
That's no more than a wild guess (which Sqad will probably ridicule anyway) but it is, at least, based upon personal experience.
Many Thanks, but there's no swelling Sqad, but whatever it is, it's not near the join between sternum and conc... - it's further over than that, more to the left.