Further update on my stupid finger. The hand specialist orthopedist said if there had been a fracture, it was a tiny one and "not anything [he] needed to treat." Super-duper sprain, but tendons and ligaments are "intact." He said to stop taping it and start using it, and referred me to an occupational therapist for a program of exercises and such. I see her on Tuesday.
Kinda like with last year's frozen shoulder, now that I know I'm not damaging it, I am happy to use my finger and to stretch and bend it, despite the pain. Since Monday, I've regained some range of motion, and the swelling is down. I can get a size seven ring on easily (not that I'm wearing a ring on that finger), and a size six over the knuckle. I really want this finger to end up its usual size six.
As for not needing to do cardio, I'm doing it (as much as I am managing to do it, sigh) to build stamina and burn off cortisol.