Yesterday I was out on a ride, and at the start of my big descent of the day, a wasp hit my ring finger. It just hung on, stinger deeply lodged into the skin. I was descending, so I kept trying to shake it loose but I couldn't risk taking my hands off the bar for long. Finally after a couple attempts, I shook him loose, but the stinger, his lower body, and a bit of guts were left behind. It was burning something fierce, but knew it was safest to just finish the descent and then clean it off.
I get to the bottom and carefully remove the stinger, and start the 15 mile ride home. When I got in, I showed my wife. It had started to swell, so she told me to get the ring off fast. I used some petroleum jelly to get that done. Now my whole hand is a bit itchy and swollen up.
So add that to my tally of exercise session gone wrong.