Cold sores will usually go away on their own without any treatment within 7 to 10 days however some cold sores may last up to 14 days.
You can help a cold sore go away faster though by applying apple cider vinegar to the cold sore 2 to 3 times per day.
You can also get rid of a cold sore by applying some toothpaste to the cold sore which will help to dry out the skin and make the cold sore fall off.