Rear camera and flashlight not working

my iPhone 5s with iOS 9.1, now rear camera and flashlight i not working. It shows a black screen while opening rear camera and after turning to front camera it is workin. Again coming to rear camera it shows a warning that "phone needs to cool down for using flashlight " even though it is in normal temperature. Rear camera shows the same black screen in all modes like vedio, slow motion Vedio. When I found the problem first, I solved it by just restarting the phone. But it came again and again. After that restart doesn't solve the issue, so I do reset setting. It worked two three times. But the problem was repeating. Now even restart doesn't makes any change. The rear camera and flashlight is not functioning any more. Is it a hardware issue? I doesn't think so, because I found so many people are facing the same thing in online discussion. So what I have to do for fixing this problem??