So here is a shortlist of all the better known, and not so well known, natural remedies for a cold sore.
Remember that some may work better than others for you individually, so it's a case of trial and error.
Salt - Salt is sodium, and good for infections, it will also absorb fluids, which is also good. For a cold sore to heal quickly it needs to dry out, a little dab of salt occasionally will help, but it will sting!
Tea Tree Oil - Tea tree is an excellent anti viral, and is used to treat all kinds of viral and skin conditions. Definitely worth a go.
Toothpaste - Contains a chemical called "sodium lauryl sulfate", not all toothpastes contain it, so look for it in the ingredients, it's normally found in plain white toothpastes. Sodium lauryl sulfate has been proven to inactivate the cold sore virus on contact. Cover the cold sore using a cotton bud, and leave it to dry.
Sugar - Used during the Napoleonic wars to treat injured soldiers, sugar draws fluid from infections, drying out wounds and promoting healing. Grind some sugar with a little water to make a paste, and apply it to your cold sore.
Witch Hazel - Excellent for drying out skin and infections, witch hazel is another of natures best healing plants. Apply some readily available distilled witch hazel to a cold sore as often as you like.
Here are just a few remedies that are known to work for some people, there are plenty more, but these cold sore remedies are well documented and will definitely help healing your cold sore.