Most fevers in children are viral in origin and take 3-7 days to subside completely. If not accompanied by any other symptoms like vomiting or loose motions or coughing and breathlessness or dullness and refusal to feed,just give paracetamol for fever and repeat every 4 hours if required. If fever persists beyond that OR if above symptoms are present,consult your paediatrician asap for investigation.