One Side of my Face Lower Than the Other?

100% of people have facial asymmetry and it's important to remember that while this can be corrected and improved, I tell all my patients that there is asymmetry to the bone, muscles etc. The same way you are right-handed or left-handed, when you smile the muscle attachments and skin attachments are different explaining why some people have smirks, dimples etc. The asymmetry is more prominent in some people than others.  There are things we can do to make things better, but at the end of the day, I tell my patients there's a 100% chance they will still be asymmetric after any surgery anywhere in the body. We usually try to make people more symmetric especially if it is something that bothers them. Sometimes people only want a facelift on one side or certain procedures without targeting both sides of the body, and this is something that is available and possible.
If you are concerned by your facial asymmetry, I would recommend that you see a board-certified plastic surgeon in your area that is a member of both ASPS & ASAPS and performs a lot of facelifts but also offers all the nonsurgical options such as Botox injectables and laser treatments. Sometimes injections and nonsurgical treatments can improve asymmetry without any surgery.  
I hope my answer helps you. If my answer helps, please take a moment to up vote this answer on the “respond” button on the top right.  Have a great day.

Facial asymmetry is a common concern and can be influenced by various factors, including dental alignment, muscle tone, and underlying bone structure. At 26, you’re likely not a candidate for a surgical facelift, but there are non-invasive and minimally invasive options to address your concerns. Consulting a dentist or orthodontist about potential misalignment of your teeth might be a good first step, as this can sometimes affect facial balance. Additionally, aesthetic treatments such as neuromodulators (like Botox) or dermal fillers can subtly enhance symmetry by relaxing overactive muscles or adding volume where needed. A personalized consultation with a facial aesthetics expert can help determine the best approach for your specific goals.

This is a great observation!
It is actually amazing, but most people have facial asymmetry. It is what makes our faces unique and different. This is why the simulated photos where they mirror one half of the face on to the other side often look quite abnormal and unnatural. However, there are certainly some people with more significant asymmetry where things can become bothersome. For these issues, consultation with a plastic surgeon can help determine if these asymmetries are within the realm of normal asymmetry or whether they are more severe and could benefit from a potential intervention.
Hope this helps!

Without a picture, it is hard to make an assessment and give any advice on what procedures can be done. Always remember two things: 1) No one stares at you like you stare at you and 2) the sides of the face are sisters, not twins, and will never be perfectly symmetrical. Going off of the first saying, as much as the asymmetry might bother you, it is most likely something that other people who met you in passing will not even notice. At only 26 years old, you are very young to be considering a facelift. If the asymmetry is seriously something you think you can not live with, then I recommend consulting with a board-certified plastic surgeon in person to discuss your concerns and see if there are any nonsurgical procedures such as fillers or Botox that can help with your asymmetry. Sometimes, correcting one asymmetry, such as the lips, or the teeth, can make everything else look balanced. But remember, “less is more,” and there is nothing more frustrating than to see young people “over surgerized” which can obliterate their natural beauty!

Everybody's face is asymmetric.  Typically there is a side there is more wide and short and a side that is narrow and long.  This is also true with the eyes as well.  Typically there is one big eye and one small eye.  This can affect the smile to a certain degree but is normal regardless of age.  If your concern is with asymmetric lips, a small amount of filler may benefit you and may provide a temporary solution.  We would recommend trying a hyaluronic acid filler as these are relatively safe, temporary and reversible. You would benefit from a consultation with a board certified plastic surgeon with knowledge of facial anatomy.

I agree you are too young for an anti-ageing Facelift.
The symmetry issues that you describe are very common so rest assured you are not the only one. My advice would be to consider balancing botox and even filler to help with symmetry when you smile.