Brief Answer:
Few possible causes

Detailed Answer:
Hi and welcome.
If there is no swelling or redness around anal area there it is not likely to be abscess, but sometimes it may present non-conventional so if fever or localized pain occur, you should see proctologist. Second, since you had trip, it is always possible that entero infections were contracted, and it ma, irritate skin around anal opening. This would however present with diarrhea. Last, it may be a anal pruritus, fissure or hemorrhoids. I suggest to apply mild cortisone ointment clean perianal area with chamomile tea and avoid aggressive use of soap. Wish you good health. Regards

---