Will my cheeks go back to normal after masseter muscle Botox?

Botox injected into the masseters causes temporary muscle atrophy. The muscles should regain their full size in less than a year.

Hello, Thank you for your question. The Botox injected in both sides of the jaw, will selectively relax the masseter, gradually making it less prominent and square. Results may last for up to a year depending on lifestyle habits but should return to it original appearance. Take care. 

Botox in the masseter muscles can definitely thin the face. I would wait for several months for the Botox to wear off. Your face should return back to its normal proportion. If you like the results from the reduction in clenching, but not the thin look, you may want to reconsider using a very small dose with your next treatment and work your way up on dose to help balance your concerns.