What is this bump under my lower eye? I had a midface lift, septal reset, canthopexy and orbicular muscle suspension (Photo)

Based on this photo and short of in person evaluation, my first thought is a fat compartment/bag. In person consultation with a board certified plastic or oculoplastic surgeon would help. Good luck.

The point is that it is impossible to know without an in person examination. Often with these procedures, one sees irregularly healed lumps of fat. They do not always heal smoothly. An examination by an experienced surgeon who regularly fixes botched blepharoplasty permits an educated guess about the likely cause of this. That will determine what strategy is most appropriate for this. Generally fixing these is done through a transconjunctival approach. You need to find the right surgeon for this. That is not necessarily the original surgeon. This is no muscle bulge.