http://tips.tipking.com/health/tip_88.shtml
That site provides some at home remedies. There is a medicine out there called..camphophenic that my friend always uses. Another at home remedy that works good right when you feel one coming on is hydrogen peroxide. Just put some on a q-tip and dab it on there many times throughout the day. Chances are it will never become a full blown cold sore. But since you already have one..give the hydrogen peroxide a chance. Should dry it up quickly.