After Botox for masseter muscle wears off, will my jaw return to my pre-injected state?

I want my face slimmer though I quite like my face shape itself. I am wondering whether botox for the jaw will change my face shape at all (which I DO NOT want), or will it keep my overall face shape just slims it down a bit? I also wonder if i were to go ahead with the procedure, after the botox wears off, will my jaw return to pre-injected state or will I experience some unintended changes due to the botox (e.g., muscle doesn't grow up as big, or skin might loosen, etc) ? Thanks,