It's a relief to pull the zipper down and escape the tight space, at least for a while. He gets undressed completely first, trying to talk himself out of being aroused and more into being happy that he's probably going to get a sweater or something similar after all. After putting his new clothes away, his cock is only half hard. That's an improvement.

He slips into the shirt first, noticing the difference. Frowning, he buttons up and rolls up the sleeves. It's not by much, but they are a bit too long. Same with the pants. Now that he's tried on something his size, he has to silently admit that clothes that actually fit him do look better on him. Grumbling without any explanation as to why, he deflates, cock following suit.

"Tch. I guess you win this time." He doesn't care to say what he's talking about before he turns around, cheeks red for another kind of embarrassment.