he was probably just irritated from a foreign object keeping him from running. i dont know how tight u had it so just be cautious when u put it on and make sure it isnt too tight, just make sure he's breathing good after u put it on, my beardie puffs his belly and beard when he is irritated alot, especially while shedding. u'll notice when he gets older he will do it alot more when growing.but just make sure the leash isnt too tight and he should be just fine, and also im not totally sure about the sunblock. i know u cant make them not lick, but.. in that case i would just be careful because even if humans injest sunblock it could make them sick.. however im sure a little bit wouldnt hurt, but im not a herp vet so im not totally sure. but the belly thing is completely normal. so dont worry.