possibly this is because of some viral infection (exanthem) that is causing him these symptoms. generally it should subside in few days.
the child would complain of sore throat
or pain in throat which is not there in your child.
most important thing in this condition would be to keep a watch on the symptoms in your child whether the fever is responding to antibiotics, whether the child behaves normally in afebrile period, is he feeding well. etc.
some warning signs like high grade fever, excessive lethargy or irritability, refusal to feed, signs of dehydration
like dry mouth and eyes, sunken eyes, intractable vomitting, intractable diarrhoea, etc should prompt you to get emergency advice.
meanwhile, you can give paracetamol
syrup round the clock 6 - 8 hourly, if fever persist along with ORS and zinc syrup to your child.
if you have any doubt about the condition you should better consult a pediatrician
today only to get him examined physically to rule out ant illness requiring immediate treatment.