Anal itch & bumb - should I be concerned?

Hi. I'm a straight male. In the past two weeks I have been experiencing an anal itch, especially at night. I also detected a small bump just outside my anus hole. I looked at the bump and there was no discoloration. The itching is the only discomfort. There has been no blood or painful bowel movements.

About a month ago I had a sexual encounter with a woman that involved her rimming my anus and fingering it. So now I am wondering if the two are at all related? Is it an STD? Did she simply aggravate the area to the point of discomfort, or a tear?

Or is it unrelated and just a case of hemorrhoids? A few days ago I stopped using soap to clean my anus when I shower and the itching subsided. Honestly don't know what the root cause is but the one symptom is my anal itching.

Please help!