If your chin is a pink white or a beige (or any variation) where the ears are naturally pink you end up seeing the blood more easily. Either way though your body temp is hot, so it's normal for them to heat up. Since they can't sweat one of the ways a chinchilla cools is by pumping blood into their ears, like an elephant. Sleeping on their side can also making the ear they are laying on hot and red until they get up.
So long as the ears go back to normal after he wakes, he acts normal, and it's not too hot in the room (above 70F) I wouldn't worry to much about it. Also laying on their side is a good sign, it shows trust, since it's a vulnerable position.