Late to this post. Hope action as been taken by now. I will only add that A needs to get over any shyness and let a doctor evaluate this lump. It doesnt sound as tho' it is in the anus...but directly above, so who knows what it could be?
The dark stools also might be unrelated, caused by diet, or blood somewhere in intestinal tract.
I am an anal cancer survivor (stage IIIb) and will be happy to answer any questions you have from my perspective. You posted here, so I am responding although as I said it may not be a colo/rectal issue.
Best wishes...
Tell A that doctors see this kinda stuff all the time. They won't even remember A's name when they leave.
Tell A to not let their pride get them killed.
Tell A to get his A into a doctor, ASAP. It might be nothing at all. It good be a cyst on the end of his tail bone It could be a lymph node. Black in his stools would most likely be from further up in his digestive track. In anycase it could be any thing best to have a doctor sort it out.
Also, Forgot too say that A has also been loosing weight and sweating a lot, They take 2 showers a day and still smell. :/