Dip some milk onto a cotton ball and apply directly to the cold sore.
Do you really need an excuse to chew on some liquorice? Well, here is a good one. Liquorice can actually prevent the cold sore virus from forming. The main ingredient, glycyrrhizin acid, is a known cold sore killer. Just make sure you are chewing on the real stuff (liquorice mass) rather than the artificial stuff which won’t prevent anything except perhaps fitting into your jeans later on.