This is the Finkelstein Test. Follow along, boys and girls:

1. Make a fist with the fingers closed over the thumb
2. While holding your hand in this position, bend your wrist towards the little finger.
3. See area indicated in yellow in the diagram above? If you get a shooting pain there (which can be bad enough to induce instant nausea) then you have De Quervain's Tendonitis (tendonitis of the thumb).
4. Get script for a thumb brace and keep the freaking thumb immobile until you don't feel like throwing up any more.
I'm told it'll take perhaps two weeks to clear up. If that doesn't happen we can explore other options.
My joy is complete.