Most of the time when I have sores on the lips I use and antiobiotic ointment like Neosporin on it. I would make sure to keep the area clean and apply the Neosporin a couple of times a day.
Don't scratch it. Sores usually heal by themselves over a short period of time e.g. from 4-5 days. Medication should be considered for the sores that take long to heal.
It depends on what caused the sore. More than Likely it is a fever blister, and there are many over the counter lip balms that can help heal it faster.
