hello and welcome to
http://androidforums.com here is a little problem solver that might help,if not i recommend join the forum for free and look up the nexus 10 forum and see what else you could try,plus im not sure if your nexus is rooted or stock,thats a main question too!!! but try this out and hope it works,good luck ------Problem: Can’t connect to camera
Some people have encountered a problem where they tap the app icon to use the camera and instead of it loading up, they get an error message stating “Cannot connect to camera.” There have also been a few reports about the camera crashing.
Workaround:
Hold down the Power button to reboot the device and it should work again, but the problem may re-occur later.
Potential solutions:
The issue could be caused by one of your apps. Something related to the camera would be the most likely, but it could be something else. You might consider a Factory Reset and see if the camera works. If it does, then one of the apps is your culprit.
If a Factory Reset doesn’t work, it might be a hardware issue and you’ll need to arrange a replacement with your retailer or Google.