Changing shutter speed on Nikon D200?

I accidentally pushed a button on the right hand side (while holding the camera) of the lens, and I think it changed the shutter speed to where it stays open for longer and i have NO idea how to fix it and really need help.

More information will be needed:
What mode are you using the camera in?

There's no switch on lenses that has any bearing on shutter speed, and in fact i'm not aware of any switches that typically would be on the right hand side of the lens (as seen from behind the camera) at all.
What is that switch, what lens are you using?

It's all about the shooting mode you are using. You can control shutter speed manually in M and S modes. If you don't want to mess with manual exposuring just switch to A mode or at least at P mode if you need to set your own white balance or other things but let camera decide about aperture and shutter speed.

Are you serious? You have a DSLR but no clue how to change shutter speed?

Are you familiar with the term "user guide" or "manual"?
It is the book that came with your camera (download a new one if you lost it) and it is something you should know inside out and off by heart.

You should also run to the library and get a few books on basic photography.

It is a crying shame to have such a nice tool and no idea how to use it.

When in doubt about settings, look for the two buttons with green dots next to them. On the D200 they are the QUAL and exposure compensation [+/-] buttons. Hold both of these down for a few seconds, and your LCD display should blink once. This will turn back your basic shooting settings to their defaults, on Program 'P' mode.

Study your manual! If the shutter speed was indeed increased, your images would be brighter than normal.

Most lenses don't have buttons, but there are two buttons on the right front of the camera body. One is called "depth of field preview", and will temporarily close the aperture to the current setting to show how it will affect out-of-focus parts of the image. The other is a "custom" button that can be set to whatever options are in its menu.

It is also possible that you simply turned one of the dials, which can change aperture or shutter speed.