I have been using arnica gel whenever I start to feel (the tingling) the begining of a cold sore. It usually stops it. Even when I had one on the inside of my mouth (don't put the arnica gel inside your mouth)...I spread the arnica gel over the area outside my mouth and it took away the pain. I learned not to use it on insect bites but it works great for bumps. I smashed my nose on a chair the other day and used the arnica gel on the outside and bag balm on the inside and it's all healed. No discoloring. I don't go anywhere without my arnica gel.

It can be found at health stores.