Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine your son and obtain a history, I can not tell you what the exact cause of his symptoms is. However I will try to provide you with some useful information.
Tics can be primary, meaning of no known identifiable cause, or secondary. Tics can be motor, such as blinking, grimacing, etc., or phonic (grunting, throat clearing). Simple motor tics are very common in younger children and resolve with age. In some children, tics are part of a condition called Tourette's syndrome, in which multiple types of tics occur for more than 1 year. Tics can also occur after viral illness and in this case these are termed secondary tics. Tics can also occur in a variety of other systemic and neurologic conditions. The majority of primary tics and most secondary tics improve with age.
The differential diagnosis to transient abnormal movements occuring in a child after a febrile illness are seizures. Other possible causes can include just habit (habitual movements), dyskinesias due to various causes, tremor, or what is termed stereotypies, which are self-stimulatory movements that can occur in children.
I recommend you have your son seen by his general pediatrician. After he/she examines your son, he/she may choose to recommend referral to a pediatric neurologist. If your son's abnormal movements are transient, it might be a good idea to video tape them so that your physicians can understand exactly what they appear like.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.