I've been trying to convince myself that I'm paranoid, yet to no avail. About two weeks ago, me and another guy "grinded" with no penetration. About eight days after, I had a small, painless bump about 3/4th of an inch away from my anus of which rarely was irritating or itchy. No pain, no blood, and it was flesh-colored and perhaps a little red. I then had a white-coated tongue a few days after, which has seemingly gone away after frequent brushing and scraping. (Perhaps incited from my frequent smoking habits?) No other symptoms.
Is it likely I contracted an STD?
The answer to your question is NO.
You describe a zero risk encounter for all STDs.