Why won't my script destroy the parts when it touches it?

Basically, I'm building a nuke where when it detonates it destroys any parts in it's radius, but if it's a player they lose HP. However, it's not working and instead leaves the parts it's supposed to destroy and destroys any parts that it comes in contact afterwards. The error says that I'm attempting to index field parent, because it's a nil value. Any help?

local explosion = Instance.new("Part",workspace)
explosion.Position = script.Parent.thing.Position
wait(0.1)

explosion.Shape = "Ball"
explosion.BrickColor = BrickColor.new("Bright green")
explosion.Material = "Foil"
explosion.CanCollide = false
explosion.Anchored = true
explosion.Transparency = 0.25

for i = 5,0,-1 do
	explosion.Size = explosion.Size * 2
	wait(0.3)
	explosion.Touched:Connect(function(touch)
		if touch.Parent:FindFirstChild("Humanoid") then
			touch.Parent.Humanoid:TakeDamage(100)
		else
			touch:Destroy()
		end
	end)
end

script.Parent.Nuke:Destroy()

local explosion = Instance.new("Part")
explosion.Shape = "Ball"
explosion.BrickColor = BrickColor.new("Bright green")
explosion.Material = "Foil"
explosion.CanCollide = false
explosion.Anchored = true
explosion.Transparency = 0.25
explosion.Position = script.Parent.thing.Position
wait(0.1)

for i = 1, 5 do
	explosion.Size = explosion.Size * 2
	explosion.Touched:Connect(function(hit)
			if hit.Parent:FindFirstChild("Humanoid") then
				hit.Parent.Humanoid:TakeDamage(100)
			else
				hit:Destroy()
			end
		end
	wait(0.3)
end)

script.Parent.Nuke:Destroy()

i don't see anything wrong, by the way @mattscy after line 19 it will still work because of line 15.