Numbness caused by holding iPhone 11 Pro

There is a "pop-up" button you can put on the back of the device, so you hold with a couple of fingers on the back instead of wrapped around the device.

You need to ask your doctor. Nobody here is qualified to diagnose your problem or give advice.

You could also reach out to Apple Support directly to get further advice. You may be able to reach them here: contact Apple Support 

Is it possible you’re playing too many games? Put it down occasionally.