if the air duct is not blocked with dust, and you cannot hear the cooling fan working, then either the power connector (a tiny 2 pole thing) has become disconnected, or else the fan is faulty and needs to be replaced.
either way, somebody who is PC savvy needs to open the laptop casing, first to check that fan power connector, and then if needed, to fit a new fan (usually easy to find on ebay) - I have done this myself, and it is not hard, you just gotta be patient and methodical.