A pimple near the mouth can be confused with a cold sore, but there are a few differences. If it is on your lip, it is a cold sore. You cannot get a pimple on your lip. A pimple forms a red bump, but not a blister. A cold sore is a cluster of tiny blisters. Pimples can hurt, whereas cold sores tingle and burn. A pimple will clear up after a few days, but a cold sore will crust over.