Do I have over enlarged masseter muscles?

Thank you for sharing your question and photos. It is difficult to assess your masseters based on the photo alone. An in-person evaluation is necessary in order to determine the strength of your muscles. If your muscles are strong and protrude from your jawline, Botox is an excellent way to weaken the muscle for a softer look. This involves several injections in each masseter, however the amount will depend on your muscle strength which is determined by your provider. Results from Botox last between 3-4 months at which time the procedure can be repeated. For more information about Botox injections, I recommend consulting with a board-certified specialist.

It's difficult to tell from your photos. I recommend getting a formal evaluation with a cosmetic dermatologist. If the masseter is enlarged, Botox can slim the jawline. See an expert. Best, Dr. Emer

Botox works well when used systematically for masseter enlargement, meaning you have to use significant amounts and you need to stick with it to see the full potential. So unlike other areas of the face like the glabella where the results are clear within a week or two, masseters take more time and commitment.  That said you don't have huge masseter volume specifically on your left.  That jawline is softer, less angular.  And like all faces, you have asymmetry to the jawline where your right is more angular or pronounced. So it is possible to use botox on this side (right) in order to restore more symmetry.  I would definitely advise you not to consider it on your left.