Wiktionary
the damage is done
phr. The harm has occurred, and nothing can be done to prevent it now; it might have been preventable, but cannot be prevented retroactively.
Usage examples of "the damage is done".
But the damage is done, lord prince, and we'll be a long time getting over it.
Since the damage is done, I must accept it, but I absolutely refuse to be left alone in the house with her.
But the damage is done, and Warren dies in 1882 still believing his potential for a brilliant army career was stripped away by a grave injustice.