The most common cause of vomiting
in kids of this age is force feeding.
If he says no, do not force him. Offer him food of his choice. Give it in attractive forms, in different plates, cups etc. Allow him to play and give him food. Do not force him at all. Instead of 3 major meals, offer him 6 small meals.
Do not overfeed him too.
Antibiotics are for bacterial infections. They have no role at all in vomiting.
As you say his weight seems to be okay for his age. So I guess there will not be any major problems.
Have a visit to your Pediatrician
, have his throat checked. Your Pediatrician will give medicines like Domperidone
to be given if he has frequent vomiting. And may be he might need a trial of short course of Medicines like Lansoprazole
. But do not administer any medicines on your own.
Hope my answer helps you.
All the best.