Painful bump on anus

Hello. I have a red bump on my anus ( I guess this is a blood blister). This is probably caused by diarrhoea (which lasted around 5 days). I felt quite a hard pain after evacuating and cleaning my anus. When diarrhoea ended, the bump appeared. It has been increasing in size during the first 4-5 days. It's now the sixth day when I have that bump. I'd say it's now 5cm X 2cm X 1 cm in size. The pain is not constant but is excruciating at times. I've been using Procto-Glyvenol cream to reduce the pain but it only worked the first few times. [ P.S. I've been having a flu now (7th day) . It started just before the diarrhoea ended. It's going quite well since yesterday. But I don't think that these could be related.]
What are the ways to get rid of this problem?
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