My 3 year old boy body feels steamingly hot yet his temp 37.3 no fever ?

Warm, but no fever: Its common for a child to feel warm but when you take their temperature, they don't have a fever. Certain areas of the body have increased blood flow which can make them feel warmer. Also, if the ambient temperature is cool or your hands are cold, the child's skin will subjectively feel warmer. There's always a chance the thermometer is faulty, so you can try taking the temp with another one!