Redditor AgentSmith420 asked the physicians of the site what the worst injury they ever saw during a routine check up. Unsurprisingly, many of the contributors weren't actually physicians and some of the stories weren't actually routine checkups, but despite this, the good majority of the responses are absolutely cringe-inducing. Perhaps the most horrifying one:
My brother once jumped on the front of my white car, grabbing the front pillars with his hands. I closed the door and caught his finger, which he pulled out quickly (as you do) but there was a tiny chip of paint that had come off the car and got lodged under the skin somehow. He must have spent a week or so chewing on it to try to get the paint out, but it just wasn't working so he went to the doctor to see if he could help. After checking it out, the doctor tells him, "The reason you can't get that out is because it's your bone."
Apparently when I shut the door on his finger, I'd broken the tip of his pinkie enough so he could see the bone through the skin and he'd spent the next few days trying to pull his own finger bone out with his teeth.
Another scary story:
You can read the rest of the answers here.