Your phone should get warm, but not hot. If it's getting hot, then there's a problem.
If you're not sure whether the phone is warm or hot, then it's simply warm. You'll absolutely know it if it's hot. Also, try letting it cool (as you've done), then put the phone back on the charger at as close to 100% charge as you can. Once you're at 100%, touch the phone, then wait 10 minutes. If, after 10 minutes, it's significantly hotter than before, then something is probably wrong, because your phone didn't go into "trickle" mode, like it should. If that's the case, I'd be more inclined to look at replacing the charger, than the phone.