Hi Sir / Mam. Pls take your son to a Pediatrician immediately. Fever is NOT the disease and it is a symptom of infection inside the body. When the body is fighting infection,  the temperature increases. The doctor has to see in person to diagnose why the child has fever. In the meantime you can give him Crocin DS syrup 5 ml and do sponging over head and body with lukewarm water.  AVOID cold water sponging.   Also keep giving him Electral so that his hydration is maintained.  Home made ORS also can be give.  Mix 1 tsp sugar and 1 pinch of salt in 200 ml of clean drinking water and give him frequently in small sips. Give bland food like rice or oats porridge or milk in small quantities.  Do not force feed.