Dear Mr. and Mrs. Fulton,
You have already done the most important thing - i.e., you have discontinued the Dexedrine. As you know, the stimulant medications (like Dexedrine) that are used as 'front-line' treatments for Attention-Deficit/Hyperactivity Disorder may potentiate the appearance of motor tics. Usually, once the medication has been discontinued, the tic will gradully diminish and even disappear. But this can take a little time, so be patient.
If the behavior does not go away, a consult with a pediatric neurologist would be a sensible intervention. The tic may be the early sign of Tourette Disorder or other motor tic problem.