Place it just before the explosion in your edit, letting the bounce set up the payoff, then follow it with the bomb has been planted sound for a clear warning. Put a Chewbacca roar after the blast to sell the reaction and close the gag.
About this sound
This 0.47-second clip captures a thermal detonator bouncing across a hard surface in LEGO Star Wars, with a light, hollow boing that repeats as it rolls. It feels tense and playful at once, like a joke with a fuse, building a split-second of suspense before the inevitable blast. The cartoonish bounce keeps the danger funny rather than frightening, making it perfect for a quick comic beat.