Don't pop it!!! It will scar if its that large. Use a hot compress on it then put something on it to dry it out. Toothpaste (not the gel kind) will work if you don't have anything else.
If you can't stand it and have to pop it - place the hot washcloth on it until it is all at the surface and use a sterilized needle to lance it. Make sure you get everything out until it is just blood. Wash your hands and face with an antibacterial soap well - at least 1 minute. Dab the area with a qtip with an antiseptic (vinegar works) then place something on it to keep it dried out - toothpaste again if you have nothing else.
I've had plenty of experiences with large ones, don't listen to these people, DO NOT pop it unless it has a visible white head on it. It'll just make it worse and last longer. Just leave it alone, clean your face regularly, but make sure you use an astrigent on it and put benzoyl peroxide cream on it at night. It will eventually go away. fricking with it will only make it worse.