<human>: This actually happened yesterday, so I'm cheating a little, but I just now discovered this subreddit, so bear with me.

So I teach a high school advanced theatre class and this week I'm teaching them about stage combat. I learned the basics in college and I thought the kids would have some fun fake hitting each other. Well, we go through punching, kicking, etc, and we get to more complicated stuff like pretending to hit a wall. 

I go to demonstrate this against the door frame of a closet. The trick is to hit your foot against the surface to make the sound while throwing your head forward toward the wall but not actually hitting it... except I wasn't paying attention to how close I was to the wall while I was explaining. I turn around quickly to throw my head forward and BAM- I actually smacked my forehead against it. The kids couldn't figure out at first whether I was just really good at faking it or if I actually hit myself. But they found out once I stood there dazed for a few seconds and started holding my head. Now I have a lump.

I went to the doctor though just in case and I do not have a concussion, so that's good...

Can you give me the gist of the text in a nutshell?
<bot>: While demonstrating how to pretend to hit your head against the wall in stage combat, I actually hit my head on the wall.