Geographic tongue appears most frequently in children and young adults. It is most common among children under age four. There is no known cause for the condition and few, if any, symptoms, aside from occasional irritation or a mild burning sensation. The bumps do grow back with time. Although these spots can last for weeks or months before disappearing, they can also recur spontaneously for no apparent reason.
The fact that your grandson was diagnosed with geographic tongue is no cause for alarm. Since it is harmless and causes very little discomfort, therapy is usually unnecessary. It should eventually resolve on its own. Try to be patient.