One of my eyelids is bigger than the other
It's always difficult to tell from a single photograph, but yes, you do appear to have asymmetric eyes. The right eye looks like it's positioned lower on the face than the left eye. The right eye also appears slightly larger and the right eyelid appears to hang slightly lower than the left eyelid.
Without a complete examination it's impossible to make any specific recommendations, but there are a few of treatment options, both surgical and non-surgical, that may help. An eyelid lift is a safe, straightforward cosmetic surgery procedure with a fast recovery time. It may also be possible to use an extremely small amount of Botox to restore symmetry without requiring an invasive procedure.
Always be sure to consult with a board-certified plastic surgeon before considering any cosmetic surgery.
Dr. Neil Zemmel has 3 Upper eyelid lift, Lower eyelid lift before & afters:
From your photo you do appear to have some asymmetry between the position of your left and right eye. Although it’s not clear if this is an issue with the upper eyelids themselves.
While I can't give you any specific advice without a direct consultation, it looks like there may be a difference in your eye size -- or a structural asymmetry in the size of your eye sockets.
When one eye socket is larger than the other, the differences in size can cause one eye to sit more deeply in the socket than the other. This can present as uneven eyelids as the upper lid will appear larger over the more deeply recessed eye.
In other cases one eyelid can be heavier than the other, which would cause eyelid droop on the eye with the heavier eyelid.
There are many other possible causes of droopy and hooded lids, including nerve issues and swelling from eye infections and allergic reactions. I advise you to schedule an examination with a facial plastic surgeon who has experience with eyelid surgery.
It's hard to tell exactly what the cause of the asymmetry is from your photo. It may be something simple with your eyelid, or it may be an asymmetry with the orbits (eye sockets). I recommend that you consult with a plastic surgeon who has extensive experience in occuloplastic surgery.
Dr. Gary Breslow has 14 Upper eyelid lift, Browpexy before & afters: