I'm having a tough time visualizing what you're doing, Trina, but it shouldn't be causing stress on your finger.
You might try a tailor's thimble. It looks like a regular thimble without a top, and it's bigger than a ring, so it might let you position the needle closer to where you want it. I use one all the time when I quilt away from myself, and I don't feel stress on my thumb joint at all.
The other source of stress is pulling the needle...sometimes that does hurt my thumb joint. I use a piece of rubber to keep it from stressing my hand too much.