Is your son experiencing problems? Have you actually had this diagnosed? A quick search indicates that this is one of those "problems" that is overtreated...
"Since the persistent duct or sinus can promote oral secretions, such cysts can become infected. Up to one half of thyroglossal cysts are not diagnosed until adult life. The tract may lie dormant for years or decades until some stimulus leads to cystic dilatation. Infection sometimes causes transient appearance of a mass or enlargement of the cyst, at times with periodic recurrences. Spontaneous drainage occurs in some instances."