K Shaffer is right that you probably will need professional service help.
However, if you want to try some things first, one of the following will fix your camera problem:
(1) If restarting your Mac doesn't fix the problem,
(2) use Apple's http://support.apple.com/kb/HT2090.
(BTW - The Troubleshooting article calls the camera an "iSight". However, after the article was published, Apple has changed the built-in camera's name on newer Macs from "iSight" to "FaceTime" and then to "FaceTime HD." Regardless of the name of your built-in camera, the same info and troubleshooting applies.)
Be sure to test more than one Apple app in more than one user account. Do NOT use the "Guest" account for this test. If you do not have more than one user account for the testing, create a new one now. If you need help, how to do it is explained in http://support.apple.com/en-us/HT201754.
A "Standard" user account is all you need for testing.
Don't bother testing Skype or other third-party apps until you have your camera working with Apple apps.
(3) If your cam won't work properly even with Apple apps, follow these instructions to completely reinstall your Mac OS.
(4) If none of the above suggestions resolve your trouble, contact Apple or an Apple-Authorized Service Provider to have your Mac professionally serviced.
Message was edited by: EZ Jim
Mac OSX 10.10.5