I just woke up and my iPhone back piece burned me and now I have a blister

Like this?

Keeping iPhone, iPad, and iPod touch within acceptable operating temperatures - Apple Support

Where was the phone while you were sleeping that it caused this? You may have been sleeping when this warning came on the phone. You probably should not sleep while in contact with your phone if it is charging.

You may want to call Apple Support to report this.

If you were injured by the device, whether or not you think it was or was not your fault, you should contact applecare and report a possible safety hazard. This is not a guarantee of any kind, but you should definitely report it.

AppleCare US phone number: (800)-694-7466

https://support.apple.com/en-us/HT201232

Scorpio1099 wrote:

Just woke up and now I have a blister. Um there should be some warning that it would get this hot!!

Hi

The iPhone User Guide includes the following warning (under Safety, handling, and support > Important safety information):

" Prolonged heat exposure

iPhone and its power adapter comply with applicable surface temperature standards and limits. However, even within these limits, sustained contact with warm surfaces for long periods of time may cause discomfort or injury. Use common sense to avoid situations where your skin is in contact with a device or its power adapter when it’s operating or plugged into a power source for long periods of time. For example, don’t sleep on a device or power adapter, or place them under a blanket, pillow, or your body, when it’s plugged into a power source. It’s important to keep iPhone and its power adapter in a well-ventilated area when in use or charging. Take special care if you have a physical condition that affects your ability to detect heat against the body. "

http://help.apple.com/iphone/10/#/iph301fc905