I think it is not a big problem and you don't need to worry about this. We are not the geometric figure. So we all have little asymmetries. One of the most common is that our eyes often appear different sizes when they smile. Maybe it has some relation with the muscles contract. Whatever the causes are, it will not bring big problems to our daily life. And you can also find slightly mismatched eyes in lovely ladies when they grin.
Hey, guy. Have you realized that our feet are slightly different in size? One is bigger and the other is a little smaller. And our arms are suffering the same question. But I can tell you that we often use our right hand to do things so the right arm is stronger than the left one. So does our eye. When we are smiling, different people may have different habits and this will result in the different muscle movement. So I think it is quite normal and needn't worry about.