Quarter size is a good size. Sounds like either a cyst or a hemorrhoid. I would have it assessed if it persists and/or increases in size with pain, drainage, etc. Try to keep this area as clean as possible; great spot for an infection to start. Avoid clothing that could aggravate it.
it could be hemerroids,go and see the doctor so he can give you cream for it
I doubt if it is serious, just keep monitoring it and if it gets worse or you have symptoms with it, then see a doctor.
Symptoms of external hemorrhoids may include painful swelling or a hard lump around the anus that results when a blood clot forms. This condition is known as a thrombosed external hemorrhoid. Or you could have the beginnings of a boil with no pain yet, especially in the summer months its very easy to get them. Since there is no pain I would just monitor it and see if it worsens or gets bigger, if you get a fever, but a boil will begin to hurt and you even may get a fever, but if there is no pain, I would just monitor it for now, of course if it restricts you from a bowel movement then I would suggest going to the doc.