Nano will not power. Case gets warm when charging.

I purchased my son an iPod nano for christmas. He had it about one month and fell asleep with it. When he woke up it would not power on. there is a very small horizontal dent in the back of the case about a quarter inch above the camera lens. When sent to Apple the indicated it was user error and would not repair for us. If I plug it into a power source or computer the case gets very warm on the lower half. I was hoping for some direction before I tear it down. Any suggestions on parts? Please help if you can.