What does "you'll shoot your eye out" mean?

This means, 'don't point your gun at your face!'

I'm PRETTY sure it means you might do something bad that hurts you? IDK?

What is shoot your eyes out mean teacher can u explain me

It used to be common for boys to get slug air rifles. Whilst they arent generaly a lethal weapon they do have a nasty habbit of ricochet off wooden boards (a common target placement) this often results in an eye injury or loss. It was so common that it became a synonym. Literally if a kid wanted a slug gun that is what people would say.