After a photo-shoot, I kept my nikon D5100 inside its cover and at the top of closet. Unfortunately it has fallen down. The height was about 7'. I did't hear any breaking sound as it was kept inside its cover. However, I checked instantly and it was seems ok. Next day when I put its power on, it was showed in the display- " Error! Press shutter release button again". What I do now?
I had this problem once.
There is nothing you can do except give it for servicing at an authorized service center. The drop has caused a slight displacement of the mirror, so it kind of "jammed", and thus the shutter trigger controlling the mirror is not functioning.
My camera was in my camera bag and fell from a meter high and this was the result. You don't have to worry, your camera is not permanetly broken, and will shoot as it used to without any problem.
It has detected that the physical shutter (or the mirror) is not quite lined up properly - that is, it isn't in the right place. This can happen if you drop the camera, since these are light-weight moving parts that might shift if the camera receives a jolt.
In many cases, triggering the shutter again will cause the mirror and/or shutter to flick back into its proper place again - hence the reason for this notice.
If it doesn't fix it, then you need to take the camera for repairs. If the camera seems OK to you, then it's up to you, but (particularly if it's under warranty) I would still urge you to get it serviced as there could be damage you can't see.