Cause of lump after Botox injection in masseter? (Photo)

It's difficult to tell from your picture. I recommend following up with your injector. Botox results resolve in 3-4 months. See an expert. Best, Dr. Emer

First, thank you for you questions and picture. Before making a diagnosis as to what this could be, I strongly recommend you return to your injector and allow them to examine the area.  To answer your questions, it is possible for the lump to be a hematoma or seroma and massaging may help; however, be gentle and do return to your injector.

It could be a couple of things. There is a chance that it may be a hematoma. A seroma is unlikely. The other possibility is that your injector may have weakened only part of the muscle and what you are noticing is the areas that were not weakened by your injection. The only way to determine the actual cause is to be examined in person. I would recommend following up with your doctor. Best wishes.