My script says `explosion` is only in enclosing function; consider changing it to local?

So in my game, there is a script but it gives me this warning My script says explosion is only in enclosing function; consider changing it to local? What should I do? Heres a piece of the script

function blowUp()
	local sound = Instance.new("Sound")
		sound.SoundId = "rbxasset://sounds\\Rocket shot.wav"
		sound.Parent = script.Parent
		sound.Volume = 1
		sound:play()
	explosion = Instance.new("Explosion") -- here is the part where it gives the warning
	explosion.BlastRadius = 6
	explosion.BlastPressure = 10000000 

I am hoping that someone could answer my question.