Mingo's injured thumb

For some reason, two scenes in the latter part of the movie focused on the fact that Mingo had a bandaged, injured thumb. The first one even begins on a close-up of it, and in the second one he complains that it's throbbing and hurting "worse than a sore tooth." The puzzling thing is that they never show how his hand got injured. Maybe that scene got cut? And it's never brought up again after those two scenes, so it seems to have ZERO relevance to the plot, in a tightly written movie where there aren't any other irrelevant detours. What's the deal with Mingo's thumb???