Wait for the device to cool down before using the flash.

Hello, I've been having a problem with my iPhone 5s for a while now. For the past 2 or 3 weeks, the external camera isn't working anymore; it stays black, and instead of the little flash icon in the photo app, there's a yellow "caution" logo saying "wait for the iPhone to cool down before using the flash," even though my iPhone is cold when I try it. I also noticed today that the flashlight isn't working either. I wanted to know if certain apps that have access to the camera can block the flash? Also, I haven't dropped it; this happened overnight. It's annoying because I can't play augmented reality games like Kazooloo since it's impossible to see if I need to turn it, and it's impossible to play without scanning. Anyway, could it also be because of the iOS 9.0.2 update that caused this? I may not have noticed right away that the flash wasn't working, but it might be related to that? And is it possible that it's just the LED lamp that's burnt out or not working, like a little bulb that’s blown? But most importantly, do you know why it says "wait for the iPhone to cool down to use the flash," when it's very cold, and do you have the "caution" message too?