Can you hear if the fan is operating or feel the air coming out of the air vent under the laptop?
Was the laptop on a hard surface or was it placed on soft material so that the air couldn’t escape from the air vent on the bottom of the laptop?
If you can hear the fan but the laptop wasn’t being used on a hard surface, try using there and see if it still gets too hot.
If you can’t hear or feel the fan since it is new (<12 months?) contact the Dell customer service in your location as the laptop will still be covered by the manufacturer’s warranty.
You don’t want to be voiding the warranty by opening it up to find out what’s wrong.