I felt change in the size of my left eye only. It became round than before. What should I do to make it just before it was?

See ophthalmologist. The problem could be with your eye itself or from something behind the eye. Before you can make it as it ws, you need to find out wht is causing it. It could be serious so it need to be checked.
Eye change. If you are noticing a change, the first issue is to see an eye doctor to determine the cause. Once the cause is determined and treated, then correcting the issue can then be considered.