Why does my Nikon D5300 exposure meter always show overexposure?

The exposure meter is always showing high exposure. Although the camera is working fine.

It sounds like you're probably shooting in an automatic mode (A, S, or P) and have set the exposure compensation to something like +1 EV. The automatic modes always aim for correct exposure, but they let you use exposure compensation to tell the camera what "correct" means to you. You can use it to keep the camera from underexposing the subject against a bright background, for example. When you use the automatic modes, the camera shows you the exposure compensation setting using the same scale that's used to display the light meter reading in manual (M) mode.

With the exposure compensation set to just +1 EV or less, you might not notice that your shots are coming out more exposed than they otherwise would.

Do this: Turn the camera on and set it to manual mode (M), and then point the camera at a variety of lighting conditions (like a well-list white wall, a darkened room, etc.) and see if the meter reading changes. If it does, your meter is probably working fine. Next, switch back to whatever automatic mode you usually use and press the exposure compensation button (it has an icon with +/-) while turning the command dial. You should see the "meter" setting change; again, this isn't really the meter, but actually the exposure compensation setting. Set it back to the middle setting.