So I ended up going to Urgent Care last night, after some pain under my ribs - mostly on the left side began to spread and get a lot worse. I have been feeling sore for a few days, but when I woke up yesterday is was notably worse and got considerably worse through the day. To whit, when I have to breath deeply - or worse, yawn - it is about as painful as most anything I have experienced - though admittedly, not even close to passing a kidney stone.
I knew I didn't have a fractured rib, because I have had those and know what to feel for. I knew it wasn't a heart issue, because I pay pretty decent attention to my heart rate and know what to look for. I was mostly concerned that it might be pneumonia or something related. But while I do seem to have pretty heavy bronchial inflammation and swollen, sensitive glands, the doctor is pretty sure it is not pneumonia - though as he was giving me an antibiotic for the bronchial infection, he prescribed one that would deal with that as well.
The problem, it seems, is something called Costochondritis, possibly Tietze, because there does seem to be some swelling. Basically, there is a major inflammation of the cartilage connecting the ribs to the breastbone. Pretty much harmless, but hurts - a lot. The cause can be nothing, some trauma or simply light exercise. The doctor also mentioned that this is more common with middle age men and older.
The icing on the cake was that while he was poking and prodding and getting me to tighten various muscles - the whole experience was exceedingly painful - he noted that I seem to have the beginning of a possible hernia on my belly. He gave me some ideas about how to deal with it, but was clear that I really, really don't want to have it turn into a full fledged hernia. Indeed he said that while that still would not quite hit the pain level of passing a stone, it would probably come a good bit closer.