Oxalate dumping after years on a carnivore diet? Interesting idea, it could also explain some of the unrelated problems that I have experienced myself in the past.
Although, to be honest, I am not sure what the problem is myself. They say that the lump is usually soft, sometimes more firm, and a bit firmer than the surrounding tissue. It's on the right side at the base of both fingers on the right hand (in the same place, oddly enough), and that the lump is usually smaller in the morning, larger in the evening. It seems that activity or food increases the size slightly. To me it almost looks like an enlarged muscle.