This is fun with terminology. The term is used to get a point of apocalyptic emphasis across, scare grandma, and yet do away with the long winded saying, "Put my ham and cheese sandwich in the microwave oven." A simple "Nuke this!" will do. Guaranteed is that no one will misinterpret this abbreviated sentence and turn on the oven gas burner. Of course, grandma may feel the urge to bean her grandson over the head with a metal hot plate! It seems that many a World War II "Flame Thrower' veteran may have used a similar meaning word with "grandma" during the Cuban Missile Crisis in the sixties!

"allow it" means to just leave something alone, or don't worry about it. People in West London say this quite often.