What is wrong with this script? The output says: "attempt to call a nil value". What does that mean?

What is wrong with this script? It won't damage the NPC. The output says: "attempt to call a nil value". What does that mean? Thanks for reading!

local animation = Instance.new('Animation')
local animTrack
local debounce = false
local player = game.Players.LocalPlayer

function onEquip()
   script.Parent.Handle.UnsheathSound:Play()
end

function onActivate()
    if not debounce then
	debounce = true
	if player.Character:FindFirstChild('ForceField') then player.Character.ForceField:Destroy() end
	animation.AnimationId = "http://www.roblox.com/asset/?id=129967390"
	animTrack = player.Character.Humanoid:LoadAnimation(animation)
	animTrack:Play()
	script.Parent.Handle.SlashSound:Play()
	function onTouched(hit)
		if not debounce then
			debounce = true
			if hit.Parent.Name:sub(1,17) == "AFK Noob Lv 1 HP " then
				hit.Parent.Humanoid.Health = hit.Parent.Humanoid.Health - 25
				if hit.Parent.Humanoid.Health == 0 then
					player.leaderstats.EXP.Value = player.leaderstats.EXP.Value + 16
				end
				wait(0.5)
				debounce = false
			elseif hit.Parent.Name:sub(1,4) == "Noob" then
				hit.Parent.Humanoid.Health = hit.Parent.Humanoid.Health - 25
				wait(0.5)
			debounce = false
        end
    end
end
	wait(0.5)
	animTrack:Stop()
	debounce = false
    end
end

function onUnequip()
    animTrack:Stop()
end

script.Parent.Equipped:connect(onEquip)
script.Parent.Unequipped:connect(onUnequip)
script.Parent.Activated:connect(onActivate)
script.Parent.Handle.Touched:connect(onTouched)