Just accept it as a new feature. Honestly I'd probably try to peel it off and make it way worse, ending up with a shirt that has a weird see-through scab. Ngl I'd just tell people it's a spill from a science experiment gone wrong and lean into the mad scientist look. At least it's a conversation starter, even if the conversation is just someone asking what that crunchy noise is.
Ugh that stuff is the worst. Tbh I had a super similar thing happen with a hot glue gun once, left this weird plastic crust on my jeans. Honestly I just wore them with the crusty patch for like a year because I was too lazy to deal with it. It never really softened up, just kinda became a permanent part of the outfit.
Wow, that crusty patch just became a built-in kneepad, right? Fashion and function! I'm picturing you trying to explain that weird plastic rock on your thigh to anyone who asked. Like, "Oh this? It's my hot glue fossil, a permanent accessory." Did it at least make a cool scraping sound when you walked?