Hello and thanks for the query
The dose of the drug in pediatrics depends on the weight. You have not explained about weight and the dose (in mg) you have take? So it is difficult to say whether over dose is taken or not.
General side effect of this medicine are nausea
and stomach discomfort
As your son is not facing any problem as said above, so their are very less chance of drug over dose. But of you feel any of the above symptoms than keep you son hydrated and stop giving medicine and consult you doctor.