Welcome!!
My kiddos are rarely nekkid so they're always in something inside, lol. It really depends though - do you keep it really cold inside? I don't think A/C will really matter that much unless it's <50 degrees. But just keep your eye on him. If he's shivering or showing signs of being cold, then go ahead and put something on. Otherwise, I think he'll be fine.
He's a cutie!!