I have an iPhone 4, the flash will not turn off. What can i do? Flash is already off on camera and i deleted the flashligth app.

Try Hard Reset -> Hold down these two buttons at the same time [Sleep/Wake & Home] the moment you see the Apple Logo 'release those buttons' allow device to reset

If still no resolution -

Restore

[back up information either via iTunes or iCloud if no recent one has been done]

Erase All Content an Settings - FIRST Set up As New - Test Camera Flash

Works? Great! - restore back up

[NOTE - if the flash does not respond again after restoring back up then sorry will have to Erase All Content and Settings Again and then the best part 'Set up As New and manually enter data/information']

If the first time done and after setting up as new and still not resolved - then Id suggest call AppleCare Support or set an appointment up with an Apple Retail Store

Best of luck

FYI, despite what Meh12 says, there is no such thing as a "hard reset". There's a reset, which is what s/he described. There's no "hard" or "soft" quality to it.