Place it right after the refusal in a short edit, then follow it with the sad violin before cutting to the next scene, or let Nelson's Ha-Ha answer it when the pout is aimed at someone else.
O tym dźwięku
This is a brief, just over a second long hmpf, a small frustrated puff of air with a light stomp underneath, voiced like a pouty protest when something is refused. It feels sulky and comic at once, the sound of someone folding their arms and turning away after not getting their way, small enough to land as a quick, playful jab.