Looks like ganglion . You can get percutaneous/ USG guided aspiration and intralesional steroid injection.
Next Steps
Get x-rays done ..visit Orthopaedic Surgeon for clinical evaluation and treatment.
Health Tips
Palomar ganglions are nutorious, they are mostly compound like honey comb . That's why they need good surgical hands to do the job for you.
Ganglions are known for recurrence.