i don’t think you can ever tell someone not to get injured. Nobody wants to get injured. Is more like you tell someone to be careful.
The phrase "Be careful" has lots of meaning behind it such as
"be careful, you might lose your valuable items"
"be careful, your feelings may get hurt"
"be careful, your bunk mates may betray you"
While "don't get injured"
Is a far more simpler phrase to use when referring to one's physical health.
I don't see an issue in how I used that phrase in this context...
However, If you want to be meticulous about how the English language is used around here, saying "is more like you tell someone to be careful" is actually incorrect. Let's see,
"is more like you tell someone to be careful" was your original sentence. A better way to put it would be,
"Be careful, would be a better phrase to use in this context."
Your entire post is also not only vague but incorrect in a sense that you're telling me that I can never tell someone not to get injured while at the same time, telling them to be careful.
The correct way to put it would be
"Everyone will get injured, you can't tell them not to get injured but you can advice them to be careful of the possibilities of getting injured."