I would recommend that you see your primary care doctor
to have this evaluated. While this may be a sign of something minor that will heal on its own, it may also be a sign of a more dangerous condition that requires evaluation. If necessary, your primary care doctor may refer you to a Ear Nose Throat surgeon
(or ENT) who can help better study the area.
Lip sores are relatively common. They are more often than not a transient thing that heals on there own. Comedones (in the same family as pimples) or cold sores or simply dry skin can all cause this.
There are some other causes of lip sores. Vitamin deficiencies can cause this problem although this is rare. The most common serious cause is actually caused by a virus. The Herpes Simplex 1 virus is a common cause than many people have. This causes sores on the lips or mouth that ultimately go away, only to recur again. Often these occur in periods of stress or other illness
The biggest concern of an skin lesion is a skin cancer. This is relatively rare. However if this persists a ENT surgeon can help biopsy the lesion and determine if this a cancer or something more simple.
Again, please talk to your doctor. Good luck!