One side of my cheek is significantly thinner than the other side, why is that? The layer of the skin feels much thinner...

I suggest speaking to a physician and seeing them in person to see if you have a condition called hemifacial atrophy which would need a series of fillers/ fat / silicone treatment for improvement, or an implant may help.  A consultaiton is needed.  Best, Dr. Emer.

In looking at your pictures, you have the entire right side of your face which is smaller/thinner. While there may be some bony component to it, it clearly looks like atrophy of the soft tissues as the main cause. (facial lipoatrophy) While the onset of facial lipoatrophy would occur on just one side of your face is not clear.

Facial asymmetry can because by several different things. It is either atrophy of the right side or it is hypertrophy of the left side. In either case I would discuss this with a board-certified plastic surgeon who can evaluate you for possible causes and suggest treatments that will meet your goals of either increasing the right side or decreasing the left side.Good luck! 

thee are known conditions that cause wasting of fat on one side of the face. YOU need an in person consultation with  a plastic surgeon.