One Side of my Face Lower Than the Other?

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.