I don't want to scare you, But hay I could be wrong, so please don't take my suggestion or idea of what I mite think it is the wrong way,
Like Welsh said, It could be your ointment..check that out too.
OK here goes, white ,dried up, could it be an infection or past healed infection, a form of mucus dried up, from a leak..ummm, did you notice prior to this, any headaches, mild fever, hot and cold,diarrhea.
Any way if your not in any sever pain that's great, please check with your doctor, Call him or her and set up an appointment.
Keep an eye on your butt, to see if it comes back (that sounded kinda funny,..

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