How to toast whole nutmeg to put in coffee?
You can break up a whole nutmeg with a hammer - just wrap the nutmeg in a kitchen towel first so none of it goes flying. Give it a couple solid smacks with the hammer, right through the towel, laid on a hard surface. This should break it up into larger pieces. (Add a couple more whacks if it doesn't, but try not to break it up too much.)

To toast the pieces, the easiest way really is just to use a pan. Don't worry - you will barely need to clean it, a quick rinse with water will do once you're done.

Toast the pieces on a stove, over low heat. Move the nutmeg bits around frequently with a spoon or by carefully tossing the pan until you start to smell them. You can also use an oven on a medium temperature (around 350 degrees F) and toast for about 10 minutes, checking and stirring them halfway through. Make sure your pan is oven-safe before you do this.

Either way, once the nutmeg smells toasted, it probably is. Remove from the heat, and add to your coffee for grinding.