iphone 5c heating issue

Define "light use." It will normally get warm when using various types of apps such as navigation or graphics intensive games.

See this article:

iOS devices: Keeping device within acceptable operating temperatures

Basic troubleshooting:

1. Reset the phone (no data loss): press both the home and power buttons for at least 10 seconds, releasing when the Apple logo appears

2. Settings > General > Reset > Reset All Settings

3. Restore the phone using iTunes, also restoring a backup

4. Restore the phone as new (without restoring a backup

Use iTunes to restore your iOS device to factory settings

This can't be determined here. If you have doubts, take it to an Apple Store or an Apple authorized service provider in your area.