Hi,

Does sound like a ganglion - that smooshing is the tell-tale (but I'm no doctor ) - they can come if you've knocked or banged yourself, and it's a natural cushion developed by the body for protection. I had one on my wrist, one on my earlobe (from earrings).

They're full of a gelatin-like substance, hence the smooshing. They stay around for a while, then vanish. Don't hurt at all - doctors make a fortune out of removing them, but it's seldom necessary.

But show your doctor, of course, sounds like ganglion, but better to be safe (and we can't actually see it.....). Not caused by RSD, btw, everyone gets a few in their life,
All the best!