Likely . Ganglion cyst. They are most likely attached to a tendon, soft and moveable.
Ganglion cyst. This is most likely a ganglion cyst. These are non-cancerous. They usually occur in an area where there is a lot of repeative motion. As a recommendation i would see your foot and ankle specialist. They can check it out and often they can drain the cyst or even remove it in the office with little to no pain.