7 year old mini schnauzer yelps when shaking head

My 7 yr old mini schnauzer Sammie started yelping when he shakes his head 3 days ago. He holds his left ear up and holds his head to the side. I have checked him over and can't find a reason for the change. We thought he may have been stung by a wasp but cant find any sign. Could an ear infection cause him to yelp in pain?