This is a very typical situation. Many people have their lower lip fuller than their upper lip. Regardless, you can augment your upper lip to become fuller. You can use injectable fillers for your upper lip to see if you like this change. The HA filler injected into your upper lip would...
It is possible that this upper lip bulge is from the muscle that purses your lips. If so, a small amount of botox can help flatten and relax this area. Hope this helps!
Johnson C. Lee, MD
Board-Certified Plastic Surgeon
Attempting to surgery alter the philtum would be deforming and likely turn out worse. Personally, I find your lip attractive and would suggest doing nothing. You have very nice lip elements. However, if it bothers you I agree with the approach that you could inject around the philtral columns...