I sleep on my left side
Everyone has eye asymmetry. Lack of sleep can affect the eyes in other ways, but it won't make one eye smaller than the other. Sometimes the eyelid can droop, however, and this can give the look of a smaller eye.Consult with board-certified plastic surgeon or oculoplastic surgeon for an evaluation of the asymmetry and to see if anything is correctable.
It would be great to see a photograph because there are several potential causes for asymmetries.Not sleeping enough may cause some occasional swelling but the effects are not permanent. Be sure to have your eyes evaluated by a board certified surgeon with expertise in eyelid procedures.