What did he throw up? If it was yellow bile, he was probably hungry. Some greys will do this and owners found that if they give them a small snack before bed, it will hold them over until breakfast. If he ate something and threw it up, it could be many things, including eating too fast. If he continues to throw up, it could be more serious but he seems to be ok so far. If he doesn't throw up again and seems fine, I would feed him, especially if it was just yellow bile.