Son is 4 year. Fever 6th day. Doc gave paracetmol & cough syrup. Blood reports show reduced wbc n platelets. Doc say just viral fever. Anythin to worry?

Possibly. While this was clearly a viral illness they usually resolve at least the fever within a week. Viruses cause lots of secretions and bacteria love standing water. Once a secondary bacterial infection takes hold, fevers go up even higher, things start to hurt asymmetrically; one ear, one side of face, one lung. Viruses are like a mist and go everywhere, bacteria just crawl, spreading from one source.