Thank you to everyone that responded. He's been resting all day, and he has significantly improved already. I will probably take him to the vet tomorrow to be evaluated just to be safe, but he's already showing huge signs of improvement. He is hardly crying at all now, and is acting much more himself. He's also becoming more active, wandering throughout the house more and he just generally seems more alert. I'm hoping it was just muscle pain from grooming (lesson learned, he will be getting baths at home from now on) but thank you again to everyone for your much appreciated advice!
My happy burrito boy says thank you!