Suggest Medicine To Stop Vomiting

my 6 year old son has been throwing up since 3am. it looks like just stomach acid. he stopped for about 4 hours during the day today and I thought he was getting better. he had a peanut butter sandwich and didn t throw it up. that s all he s had today though besides water. he threw up just a little bit ago and it was more than just acid. I m wondering if there is an over the counter drug I can give him or should I go to the walk in clinic? or should I just wait it out and hope it goes away on it s own?