I believe you are from India, your doctor has treated your child adequately with a good antibiotic, paracetamol
for fever and decongestant for nasal blockage.
Since blood reports for malaria
are negative which is common in India. other chances may be it is viral illness. Antibiotics wont work in viral fever
, you need to treat the symptoms, it will be alright in 5 days.
If the fever persist your doctor may give your child's blood for microbiological culture and can change the antibiotics he is receiving.
You havent mentioned your child's age. Give a good health diet to him, give plenty of water, if fever is very high you may need to give cold
Iam sure he will be alright.