I had perianal abscess surgery one month ago and my doctor said you don't have to take any medicine but my wound is not properly healed and suggested for sitz bath with betadine solution.

Use warm soaks. Superficial abscesses not involving intraperitoneal area but rather perianal, when drained, can be managed without medicationsl . Rather warm soaks to area allow inflow of blood supply to enhance healing. Any source of warm soaks including baths will enhance healing of surgical site.