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.