What Does Hard Lump On The Side Of Penis After Having Oral Sex Suggest?

About half an hour after my first experience of having oral sex done to me, I noticed a hard lump on the right side of my penis about 1cm below the head, on the shaft. I have to retract my foreskin to properly feel it, but it is noticeable without pulling my foreskin back... It almost feels like a rock solid vein, and is about 1.5cm in length. It is skin coloured, is not painful, and has not caused my penis to 'grow' a different direction. What could it be?!