Answer:
It'll even out if you leave it long enough. Sometimes you might have to trim the left side to keep it from outgrowing the right.
Very rarely does the hair growth on one side of the face match that on the other. In the same way as the hair on one's head parts naturally on one side or the other, so does the hair on one's face... and its not just the hair. If you really study your own face in a mirror you will see that the left half of your face is quite different from the right half.
Other than getting major plastic surgery, which would not be a permanent solution, there is nothing any one can do about funny facial hair You just have to live with it or shave.
Many guys just don't have full beard growth. If you are fully grown, and have bare or patchy areas, or thinner areas, it likely won't improve. Maybe having it longer will help.