Question on ethics or rules
East reneged (played an out-of-suit card when they had a card of the correct suit), but fixed the error before the next trick; since they're the defender, two things happen:


East's small spade is left face up on the table in front of East. It's a "major penalty" card, and must be played by East as soon as it is legal to do so, on some future trick. (Furthermore, if that card is still face up when West leads, you get to pick whether West must lead spades for that trick, or must not lead spades until he loses the lead.)
You can change the card you played, so that you played the king of clubs and took the trick.


If the declarer made an error (you as South, or you playing the dummy North hand), then you get to fix the error, and everyone playing after the corrected player may also change their play. Declarers don't get penalty cards.

Short Answer: you get a chance to take the trick, and there are additional penalties for East playing incorrectly.

If it's an informal game, then maybe you don't worry about the penalty card (how friendly is your game?), but you definitely get to change your play.