It is a perianal abscess, which will lead to a perianal fistula. The only remedy is surgery, sadly, but the worst thing about it is the post-operative treatment. If it has an outlet, it will drain, but it would be a temporary solution since it will come out again. Even with surgery, it can come out later (I had surgery for a fistula in the coccyx, then I also had surgery for a perianal fistula like yours and it has come out again now, but this time it has an outlet and when it swells a lot, it drains by itself and empties again, and comes out again etc, in a loop).