You definitely require a local examination. There are two possibilities that I can think of here.
1. There may be a chronic local abscess
that is recurring in or around the anal region, or the gluteal region or the tailbone region itself.
2. There may be external hemorrhoids or piles that are being secondarily infected by bacteria.
You require the right management. Please do not think it will just go away. If it had to, it had been gone by now.
Please get a local examination done as said and get treated early to prevent complications.
Hope this helps.