"This is what happened to my tips of fingers. Mine started 2-3 months after I bought it. It’s not like you can return it because you owe too much on it. My fingers feel numb and burn constantly and hard to text now. I really don’t know what kind of phone to get now."
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Perhaps this is a Faulty Device?:
It’s been less than a year, according to your post. You have a one year limited warranty from the Manufacturer: Apple. So, start by contacting Apple***, and request that a Genius Bar Appointment be Reserved. You would take this to your Local Apple Store, during which the battery and all other necessities would be looked at. Rather than troubleshoot this, have Apple look into it. In the mean time, just let the device sit in a safe non-active location, leaving it out of direct sunlight, and out of the corner of the room, and out of inclosed spaces.
***Info on Contacting Apple: