I got a fancy rat yesterday with my boyfriend at petsmart. he keeps making a weird noise?

yesterday, after about a month of thinking about it, i finally got me a fancy rat from petsmart. i know its not the best place to get animals from but he was so cute. and hes at really great home now with a tons of stuff and lots of love :P most of em were really big but i got the smallest one because it ran up to me first. his name is oliver but i call him ollie hes super sweet but he keeps making noises that kinda sound like monkeys. its like squeaking sorta bu more throaty and it sounds like hes chewing something. i think hes grinding his teeth. idk. i got him a activity ball too and he just gets in and sits i know it'll take him a few times to figure it out. but anyway what are those weird noises hes making? and he sneezes too. is he sick? my parents don't know about him yet either. but they usually freak out then get over it when i get animals. if it sounds like hes sick i can bring him to my cousin whose a vet but. the weird chewing noises are weird is it good or bad? i read something about bruxing or boggling. but i cant seem to find anything explaining what it is or why they do it.