Sometimes it can happen that apropos your iPhone camera inoperable. Not to worry, you can fix if something software.
The first is to reboot the phone to check if the camera software is reactivated. We can turn off and on again or we can do a hard reset.
If after this still does not work, try to access the section where access restrictions to the camera and other functions of your iPhone is turned off. We are going to Settings -> General -> Restrictions
If activated you will see that have allowed the camera, you have to activate it if it is disabled and we can use it. In this case you must restart the phone, avoiding problems using the camera.