Your son most likely has viral fever
which shoud go away in next 48 hrs.
Your doctor is justified in not starting any antibiotic in the absence of a clear indication.
If fever persist for another 48 hrs or so please discuss with your doctor about doing further investigations like Typhidot-M test, repeat malaria
test, blood & urine cultures & also repeating blood counts along with ESR
In the meantime continue crocin
& encourage liquid intake.
Hope you find the info useful.
Wishing your son a speedy recovery.