Pimple on my anus... small in size but painful during useing bathroom.... please suggest....

Peri-rectal issue: OK..well..something like this could be just that..a pimple. But..it could be the start of a peri-rectal or peri-anal abscess. A pilonidal cyst is not out of the question either. If it does not resolve in the next week, or grows in size, or starts expressing pus or becomes more painful then you should see your primary and probably have a colo-rectal surgeon evaluate you.