All smartphones warm up a little during intense use. This is quite normal and nothing to be alarmed about. During intensive use, the phone draws a lot of power from the battery and this causes it to warm up.
What is abnormal is where your phone heats up tremendously and becomes hot. Sometimes, the only thing to fear is a burning sensation when in contact with your body. In worse cases, the phone may shut down, become unresponsive or reboot.
In the worst case scenario, the device may combust – burst into flames.
Also, note that heat drains the battery of your phone faster. The hotter it gets, the faster your battery drains, so you get the most out of your battery if you keep your phone from heating up too much.
What To Do If Your Phone Gets Hot During Use
1. Put it down a while and let it cool down.
2. Turn off WiFi or 3G/4G data. Internet usage are key power drainers in any smartphone. By disabling your internet connection, you cut off this factor, and of course mostly likely will put down your phone 
3. Don’t use your phone in extremely hot conditions e.g near ovens, in direct, scorching sunlight.
4. Turn off battery draining apps. Those are usually apps that run in the background and using your internet connection. These may include Map apps, email apps, and ocial networking apps.
5. Sometimes, the problem is a rogue app – a badly written app – running in the background. Find it. Kill it. Uninstall it. Do not be merciful.