Flash is too bright on my camera?

On my Nikon D200 DSLR people are complaing that the flash is way too bright and litteraly blinding, how can I turn it down? I'm sorry for my little knowledge of this as this is my first time using any sort of flash on a dslr, this also is the built in flash, not a speedlight

Added (1). Its that the flash is bright and hurting peoples eyes when i take the photo

You need to get a bounce, or speedlite and a bounce, or a diffuser.

something like this perhaps
http://photojojo.com/store/awesomeness/pop-up-flash-bounce/

I'm a Canon girl, but I assume Nikons, too, let you adjust the flash output. Read your manual to learn how to do that. Actually, read your manual anyway!

However, an external flash is Way better because of the options it gives you (such as bounce, diffuse, filters, etc).

Are the flash photos properly exposed, or are you simply dealing with people that complain?

Read the manual. If you can't find it, try stepping back.

The brightness of the flash is not adjustable. The flash is controlled by the camera that adjusts the length of the flash so it sends out the appropriate amount of light to illuminate and correctly expose the subject.

Use a hot-shoe flash and bounce it off a light coloured ceiling or wall. That way they do not see the actual discharge lamp as it fires.