I had stretched, warmed up, and was woolgathering as I loaded plates onto the incline press. Woolgathering: this is a lovely term that essentially means doing something mindlessly, on auto-pilot. Goes back to the days when people plucked bits of wool from brambles and branches where the sheep hung out; apparently there was enough of the fur to justify collecting it. Not the most intellectually-challenging activity.
Normally, I am more focused when I do weights. I don't listen to music, I tend to do reps slowly and carefully, watch my posture and form, all the good stuff, but for some reason I wasn't paying attention, and thus managed to bang the rim of the 45 I was moving into the side of the bar upon which I was about to load it.
Which would have been no big deal, save that between the plate and the bar, was my left thumb. Whacked the middle joint a good one, Ow, crap–!
Didn't drop the weight, got it loaded, and after a moment to reflect upon my folly, went on to finish my work-out. I did pause to run cold water on it, then iced it when I got home and taped it. I don't think I broke it, and there will be a little bruise to go along with the soreness to remind me of my inattention.
The lesson for today, children, is ... mindfulness. It is better to pay attention to what you are doing, especially when performing it incorrectly is apt to cause injury, pain, maybe death, all like that.
A word to the wise ...