I came across this line while reading the Novel Kane and Abel by Jeffrey Archer.
In the novel, Abel uses this line when he sees his hotel burned to the ground.
I searched a lot but found just one link in which explanation is given as follows , which is still not clear to me :-
Madry Polak po szkodzie
Equivalent: Lock the stable after the horse has bolted.
Literally: A Pole is wise after the damage has been done.
Any explanation is much appreciated.
Locking the stable (or barn door) after the horse has bolted is a common English idiom for fixing a problem when it’s too late — the damage has already been done.
The Polish version states it more simply: people only learn (become wise) after they made a mistake.
If this were being said by non-Polish people, the reference to Poles might be an ethnic slur (in less enlightened times it was common in America to use Poles as the butt of jokes). But since this is actually a Polish proverb, and the character is Polish, I believe it’s just using “A Pole” to refer to people in general.