Debbie,
Here's a quote from Chicken Wrangler Sara and her pre-vet school Rachel: 
"After checking with Rachel, I believe the quail may have an ear infection - or it could just be a bird brain issue.  Not sure.  We've had some with balance issues as well.  Sometimes they do fine.  Other times, they die.  That is why I don't get too attached to the quail."
Hope that helps you solve the issue of why your quail chick tilts his head.