Honestly, I don't see a dramatic difference, but if it bothers you...
Usually, unilateral work is recommended to correct imbalances in strength - basically, choosing movements that require each arm (in this case, leg) to work independently/without help from the other.
Lunges, step-ups, unilateral leg presses and extensions are good choices of movements to balance out strength.
As far as size/shape, I wouldn't be overly concerned with that.
Even top pros have slight size imbalances between right and left sides.
Many times, you notice it with upper arm development, but it's not always appendicular; some people have an imbalance between right and left pectoral, traps, etc.
Although it probably drives you nuts, believe me that most people will never notice since few people are as observant as judges in a physique contest.
Regardless, you're worried about a part of your body that isn't even seen much wearing average clothing and swimwear.
And, if you plan to compete at some point, I still wouldn't worry about it unless it becomes worse/noticeable.
