I'm sure he damaged his ulnar nerve. I did that myself years ago, and everything he described is exactly how that feels. It's one of those things that when you've done it to yourself, you recognize it when it happens to others. Essentially it's what happens when you bang your funny bone, but several orders of magnitude worse.
It's something that can feel better in days or months, and heal on its own or require surgery. I couldn't feel my pinky and ring fingers for about a week, and the tingling was there for months. It can reduce grip strength, and could affect shooting if it's on his shooting hand. It's a much worse injury for quarterbacks and pitchers than it is for basketball players, however. It can also have recurrence with further bumps, and get progressively worse over time with repeated injuries.
I'd expect he'll play through it. If he sits out, that's a very bad sign in my opinion, since that means he's hurt it pretty good. If he does play, watch for him shaking his hand in the air -- that's a sign that he's having that tingling/can't feel his fingers closest to his pinky.