When I turn my headlights on I hear a knocking noise coming from under the hood

Since the vehicle is under warranty, the dealer will be able to assist you. It is important to become an expert at causing the issue to recur so the technicians can understand what is happening. The first thing your shop do is isolate the noise. You can do this by having a friend turn your headlights on and off while you listen under the hood. Is is more safe to perform this inspection with the engine off, if the lights will still make the noise.