While it’s hard to tell from your photos, this does not appear to be an area treatable with Botox. Botox is limited to treating the area between the brows, the forehead and the crows feet on the outer part of the eyes.
Masseter botox works by causing atrophy to the masseter muscle. This results in a thinner looking face because the muscle isn't as bulky. It does not do anything to the bone.