After the botox treatment for masseter muscle, I massaged accidentally. Would it alter the results?

The master muscle is the strongest muscle in our body per each gram of muscle tissue. To cause any problem would be nearly impossible since, most likely, the pressure you had used created much lower forces than you would see during mastication...chewing. If that was a problem, no eating or gum chewing would be a allowed after the injection. Good luck!

The reason we don't massage Botox is so that the fluid injected doesn't migrate to an area where we did not want it.  There is no way to say for sure if you did anything negative until after the period of time it needs to kick in.  In this case if it was over 2 hours after and the fact that it is in the masseter is unlikely to have any issues.  Good luck with your treatment.