I have asymmetrical cheekbones. One sticks out too far. What I could do to change this?

The thing you have to decide is which cheek side do you like the best. In other words, should you reduce the larger side or augment the smaller side? Cheek augmentation uses a small implant while cheek reduction is done through either burring or an osteotomy depending upon where the asymmetry on the cheek is located.

 Aesthetically speaking, I do a great deal of Cheek Augmentation with fillers (I prefer Perlane) and Cheek Implants.  Every face is asymmetric including the cheek area and this alone is not an indication for cheek augmentation.  Facial beauty, IMHO based upon my book on the subject "What's Your Number..The Palmer Code" is not based on facial symmetry but the appearance of ideally sized and shaped aesthetic features, of which the cheeks are the most important.  Without pictures, of your face, there is no way for me to tell if your cheeks are or are not aesthetically ideal.  Hope this helps.