Dialated chinchilla eyes

My chillchilla used to be quite nice but lately he's been growling and barking? Lol He gets really mean when I come within 2 feet of his whole cage. His pupils are very large and kindof blue. He stands up and lunges his head at me to bite when ever i try to pet him. But his behavior changes drastically in such short time. He will be very angry one second, but once I can pet him, he is very nice and social with me when I hold him. He acts completely unscared until I put him back in his cage. He also grinds his teeth when he is angry. It's a really loud noise and sounds like he's chewing on pebbles. I have never been abusive towards him or hurt him and have not noticed any injuries on him. Do you know what may have caused him to become so aggressive so suddenly?