Fistula is a abnormal track connecting your outer skin with inside your anal canal. This abnormal track need to be excised/ separated. This needs a Surgical treatment. And the Problem with this fistula is, because of contaminated area, recurrence is common (5- 10%). You should go for surgery after defining the fistula tract/ extension/ location by doing a Trans Rectal Ultrasound ( TRUS) and if required a MRI PELVIS.
Next Steps
you can go either of one , it depends upon surgery / Surgical skills / Type of fistula and not the method you choose.