My camera is taking dark pictures?
I dropped my D3100 Nikon camera the other day and now when i look through the camera hole it is almost solid black. It is also blurry. You can see things just barley. It also says "press shutter, release button again." I yellow letters (When you look through the camera hole) it says iso auto 900.
Needs servicing
You are grossly under exposing the images
Are you using the cameras fine light meter?
Do you know, that if you shoot in low light that the slow shutter speeds will produce blur because the camera is moving while you are exposing the image
Here is how you will best learn to use your camera, balancing the ISO, shutter speed and lens aperture.
Links to how all that works
http://camerasim.com/slr-camera-explained/
http://camerasim.com/camera-simulator/
No, YOU are taking dark photos… The camera is probably fine…
It sounds like the shutter or the mirror is stuck or even damaged, I think you've broken it by dropping it so I'd take it to your nearest Nikon repair center. Definitely sounds like a hardware fault as opposed to software issue or even your own technique. Don't worry, I'm sure they will be able to fix it for you.
I'm 99.9% certain that you damaged your camera when you dropped it. I'm 100% certain that if you'd had the camera's neck strap around your neck you wouldn't have dropped your camera.
Look in the back of your Owner's Manual for the list of Authorized Nikon Service Centers. Find the one closest to you and send your D3100 in for an evaluation. Be forewarned that any repairs will be at YOUR expense since damage caused by dropping or otherwise abusing the camera is NOT covered by the Nikon warranty.
Once you get your camera back keep it safe by using the neck strap. So far, in 40 years, I've never dropped a camera. Its either hanging around my neck by the strap, securely attached to my tripod or safely nestled in my camera bag.
NOTE: Its called the viewfinder, not "… The camera hole."
The key word here is "dropped". If this was not happening before and it is after, the camera needs servicing. If you bought a special warranty, even a drop might be covered. If not, the repair will be on your nickel, as a regular warranty does not cover abuse.
Yeah, definitely go get your camera fixed. When you dropped it, you must've somehow damaged it. Sorry.
Put the exposure up, by putting the aperture down, the shutter speed up, or the ISO up. If it still doesn't work, I would get it checked out. Make sure nothing if covering the lens as well!