My mom said she will slam my head into my computer if I don't get off it. I'm not too worried though, I think she is just joking.
Violent Threat Dismissed as a Joke
Explanation
The humor comes from the casual way the person talks about the violent threat of being slammed into a computer, followed by dismissing it as a "joke". This is funny due to the mismatch between the violent situation described and its dismissal as if it were a common occurrence.
Your king
You made my nose bleed