you can't unring a bell

You can't unring a bell (you cannot undo what has been done, so you must live with the consequences of your actions.) —
сделанного не воротишь; что сделано то сделано; ...

Example: I'm glad you apologized for what you said, but that doesn't really take the words back. You can't unring a bell.

see also
ср.:
[слово не воробей — вылетит не поймаешь]
что написано пером, не вырубишь топором

--------
Once a bell has been rung, it is heard — and people are already responding to the sound of the bell. You can't then take the sound waves back and pretend that the damage has not been done. (WordReference)