Hi,
Welcome to the ehealthforum. I am glad to help you out. Cold sores are caused by the virus, Herpes simplex. Normally, the cold sores do produce the blisters and these are usually around the lips and mouth. However, in your case they may not be forming the complete blisters and disappearing before. Actually, there’s no treatment for these cold sores and they tend to get healed by the body’s own defense mechanisms. Hence, you need not worry about the same. I sincerely hope that helps. Take care.