Cover for lens won't close - Nikon Coolpix 4800 Digital Camera

That is a lens error. Please see this video for troubleshooting steps.

Lens covers are delicate things. A bit of dust or dirt inside and the the springs can't do their job. When cleaning doesn't work, to repair this I remove the lens cover and shorten the springs by cutting off a bit and then reattaching them. A small bit of mollyd to lubricate helps too. never use oil or silicone.

Stuck automatic lens covers are fairly. But usually it's very easy to fix, without even opening the camera. See this link for troubleshooting steps for this problem.

Make sure the battery is installed correctly.Try opening, then closing the cover to the memory card and battery compartment while holding pressure against it until you hear it click closed. Then try to power it up. The camera will not power up if the cover is not properly closed.

Lens block is faulty you must replace it with a new one

Not sure if you mean the automatic lens cover, or the actual lens shutter, so here's fixes for both:
Stuck automatic lens cover
Stuck shutter

Here's an article I put together for repairing lens covers. Good luck, and try to keep track of where each part goes.

Today's digital cameras are smart. They won't operation if the lens cover is in place (or closed), nor if there is no memory card in place. So ...

1. Check that the lens cover is "open" or removed. (Open and close several times to be sure it's not stuck or jammed.)
2. Then check that you have a memory card inserted, AND that it is properly formated (that is, that it is prepared to record images; see your instruction manual for details.

I hope this helps.

to open them completely simply push them with your finger. try doing so also when closing them. i have the same issue sometimes.

I have a solution posted in doc "nikon s5 s6 lens cover error repair.doc"  uploaded on site http://www.esnips.com/web/papputatiyasStuff    It will be helpfull for you. Its is a step by step solution with images.
Regards Mukesh