A month ago I put a small amount of Vicks vapour rub in my anus now my anus is all swollen and pimples outside, what should I do?

Stop using vicks!!! Vick's vaporub should never be placed internally anywhere including the nostrils, vagina , mouth or rectum. Stop using it that way.
Hydrocortisone. Be very gentle about washing. Rub in some otc Hydrocortisone cream twice a day. Preparation h could also be used instead. After a bowel movement gently clean with some hand cream.