The literal translation is "do it one time", but it's used in a more general way, meaning "do it just once," or "don't do it again."
Here are some example sentences:
* "Aik se bar ker, aur mat karo" - Do it once, and don't do it again.
* "Aik se bar ker isko check karo" - Check it one time.
* "Aik se bar ker khana kha lo" - Eat your food once."
It's important to note that the exact meaning of "aik se bar ker" can vary depending on the context.