Hi,
This is most likely to be a Perianal Hematoma, or external piles.
These are not really hemorrhoids but a collection of blood under the skin, such as you get in a bruise. They generally clear off by themselves without any problems. Give about 10 days for it to go.
However, you must report tot he doctor if it stays beyond 10 days without decreasing in size, or you have altered bowel habits.
You can read up here:
http://www.netdoctor.co.uk/ate/digestiveandurinary/202145.html
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