A cold sore is a blister. Its symptoms are extremely trying, especially when the cold sore is located in a sensitive area, such as the corner of your mouth or right under your nose. Often, a cold sore accompanies a cold or the flu, which means that when the blister is located around the nose area, it is constantly being aggravated every time the person blows their nose. The pain of a cold sore symptom alone is challenging, but when you take into consideration external factors, it can be even worse. If the sore is inside your mouth, then it may be a canker sore.