Am I using tick() incorrectly? How do I reset it for my function?

game.ReplicatedStorage.ScreenShake.OnServerEvent:connect(function(player, duration)
	local humanoid = player.Character.Humanoid
	local timer = tick()
	if humanoid.Health <= 1 then
		return
	end
	while timer <= duration do
		print("d")
		humanoid.CameraOffset = Vector3.new(math.random(-2, 2), math.random(-2, 2), math.random(-2, 2))
		wait(0.2)
	end
	humanoid.CameraOffset = Vector3.new(0, 0, 0)
end)

Problem is when I print (timer, duration) it will print the timer as like a number in the 1,000,000s and the duration as 2. How do I make it so that timer is the time that has passed since I started the loop so that when it passes the duration the camera will stop shaking?

P.S. using this so I can just fire it to the server whenever I need it shake.