Can I replace the outlet myself or does this seem like a more extensive issue?

So the other day I had a space heater running in a GFCI outlet on one side of my house for about 2 hours. All was fine with this outlet and the space heater. But I went across the house to plug in my phone, and the top receptical on a non-GFCI outlet in that same circuit was warm to the touch. Not hot. None of the other outlets in the circuit had this going on.

When I turned off and unplugged the space heater the receptical cooled within 5 minutes or so, stayed cool to the touch. A receptical tester didn't indicate anything wrong.

Would it be safe to assume just that outlet is faulty and needs to be replaced, or should I have an electrician out to assess and fix it? Or is this normal, given I was using something that pulls a lot of energy? I use this circuit a lot as well as that outlet specifically and this is the first time I've noticed this.