PET scan is a non specific indicator of increased metabolic activity of any cause. It is elevated in several conditions such as inflammation, increased activity of muscle and malignancy but can not specifically differentiate between them. If there is nothing there on CT or MRI it may not be cancer. I would not panic and wait for your ENT expert to investigate it or continue to observe it.
I had false alarms myself with PET scans as they are often misleading.

I Brook MD http://dribrook.blogspot.com/