Vise has an insert called a semi that has a "bump" inside the insert, rather than at the end. I wonder if this is what you're referring to. We have lots of bowlers who think they are more comfortable.
Either way, it's not a bad idea to get the span and pitches checked because our hands change over the years of bowling. It could also be the start of arthritis in those joints (due to wear and tear over time). I have some in those fingers from 20+ years of bowling. On those days when it's painful I try to remember to take some ibuprofen an hour before league to help. Arthritis in a "new" spot is especially painful, but usually gets somewhat less after some time passes. Those of us who bowl for years should expect this problem, and feel extremely lucky if you avoid it.
Is there swelling on the top of the joints, or do they seem to be losing some flexibility? If you've bowled for several years I'd be willing to bet on the arthritis thing, but an x-ray should reveal it starting in case you really want to know. Hopefully you don't have any ligament damage because that can take awhile to heal since we're always bowling...
