So we have to believe he finds a way to shift properly without pain?
Most people had the experience of pain starting after a muscle is colder. When still hot and in use, a mild injury can manifest after some rest.
But I don't remember a debilitating injury getting fine enough you get functionality back without pain.
What I experienced is trying to use other muscles and movements to compensate and avoid immediate and intense pain. But it's not always possible and not very efficient/fast/precise.
In the case we have here, it might be possible to shift without using some fingers. Or shifting with the palm, or with the hand in unusual positions, or without changing the elbow angle. That to lower the pain bursts and intensity.
Now, although I know injury is an integral part of sports and an athlete's career, I admit it gets overused in sports anime.