Phone charger gets really warm while charging?

This has never happened before, or at least this is the first time I've noticed it. I recently got a new iPhone 8+ less than a week ago, and last night I noticed that when I plugged it in, the spot where the charger plugs into the phone got rather warm. I unplugged it and used a different charger, and it didn't seem to get hot when I charged. The charger I was initially using was not the Apple charger that came with the phone, but it seemed to work well with my previous iPhone 6s+. The charger was plugged into a power strip with numerous other things plugged in so I thought it was that at first but I tried it in another wall socket and it still got warm, but not as warm. Help? Could this damage my phone?

*I also tried it with my mom's iPhone 6 and it didn't get warm at all.

Maybe a dodgy phone take it to Apple shop I had same they said it's cos I was playing games but it shouldn't get roasting hot hope you get a new phone

The charger that comes with the device provides proper power to charge the device. A different charger might not provide as much power as the device uses, so the charger and device can get hot. It sounds like the new phone uses more power than the old one. It's best to use the charger that came with the device.