Wrong Medication given to my son

On the 23 Sep 2017 I took my son (Sifiso)to our local clinic (Sebei Motsoeneng), as he was vomiting. The nurse asked what was wrong and I explained, then he was a medicine. I gave him as prescribed and he continued vomiting, then on the 02nd October I took him to the Doctor that's we're I was told the medication given was wrong. My concern is how sure can I be that my son is ok after having the wrong medicine, and that what if it has caused any damage inside.