I've Been Wearing One Contact in my Left Eye and Now my Right Eye Droops?

This is not a problem that you should look to your optometrist for care.  This is a condition that can represent medical concerns.  Therefore it is appropriate to seek out an actual medical assessment.

There are various causes of eyelid ptosis (droopiness). Among them are long-term contact lens wear (especially hard contact lens).  You should an ophthalmologist or oculoplastic surgeon for evaluation. Eyelid ptosis surgery can be performed to lift the droopy eyelid.

Droopy eyelids can have many causes. There are now new techniques especially for lower lid support that minimize risk such as lateral access only techniques. If it is your upper lid that is droopy that can usually be repaired by a fairly straightforward procedure. Submitting a photo with more information would be helpful. 

The long term use of hard contact lenses can be a cause of ptosis.  You should be examined by your ophthalmologist.