Player is nil in a function?

So I got this annoying problem I've been trying to solve for more than an hour now.

Here's the code:

script:WaitForChild("DetectLevels").Event:connect(function()
    local IsInLight = false
    local function CheckForLight(Player)
        print(tostring(Player)) --Firstly prints my name and then prints "nil" a second time
        for i, l in pairs(game.Workspace:WaitForChild("Lights"):GetChildren()) do
            local distance = math.floor((game.Workspace:FindFirstChild( tostring(Player) ) .HumanoidRootPart.Position - l.Position).magnitude)
            if distance <= l:WaitForChild("Range").Value then
                --IsInLight = true
                return true
            end
            wait(.1)
        end
    end

    while wait(1) do
        for i, v in pairs(game:GetService("Players"):GetChildren()) do
            if game.Workspace:FindFirstChild(tostring(v)) then
                CheckForLight(tostring(v))
                print(tostring(v).." is in light: "..CheckForLight())
                wait(.1)
            end
        end
        wait(10)
    end
end)

I'd really really appreciate any sort of help!