system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do I enjoy small amounts of pain, especially from poking at my gums or biting my inner mouth areas?

I find myself, almost daily, poking my gums with a toothpick or other objects with a pointy edge. Often I'll poke until my gums bleed because I enjoy the sensation, even though it causes pain. There are times when I'll bite the inside of my mouth below my lip or on my cheeks because of a similar pleasure/pain sensation.

I've spoken to others who also feel the same way and cause themselves the same pain. I would love for someone to explain why I enjoy this type of self-harm?
gpt
Endorphins are released every time we are injured. Endorphins act as natural painkillers similar to morphine. 

This is evolutionarily advantageous because when we get injured, we don't want to be wallowing in pain in a situation where we may get even more injuries. The endorphins allow us to temporarily ignore the pain so we can get ourselves out of the dangerous situation.

I think you just got used to enjoying the small rush of endorphins that occur when you injure yourself. Make sure to control yourself so that it doesn't become an addiction and clean off your wounds so they don't get infected.