You were born this way. Hey and you are married if it doesn't bother your spouse and it isn't very noticeable it shouldn't be something you dwell on. You can bench and do dumbbell pecflys with heavier weight on the less built side if it bothers you.
All of us have some degree of asymmetry. Someone told me that as your pecs grew, the asymmetry would become less obvious. I don't know if it's true; mine is still obvious to me (but, others don't see it).