How can my eyelid droop be fixed?

Hello,I suspect you have Horner's syndrome.  This is a loss of stimulation to the eye from the sympathetic nervous system.  The thyroid surgery may have injured the nerves that control the sympathetic nervous system to that side of your face.  In addition to the lower eyelid, you may have a smaller pupil and loss of sweating on that side.  There is no cure for this condition, though it may go away spontaneously if the nerve injury was minor.  In the mean time, you may benefit from using an eye drop called iodipine.  This will temporarily stimulate the muscle in your eyelid that the sympathetic nerves are supposed to stimulate.  This will probably be your best treatment for the short term and may work just great for your wedding.  In the long term, if the condition persists, you may consider having ptosis surgery to lift the eyelid.