Hi. About 2.5 Years Ago, I Noticed A Little Lump/bobble

Hi. About 2.5 years ago, I noticed a little lump/bobble on my penis shaft about 3mm accross, after having a good old feel around. You cannot see it, only feel it. About 6-7cm above my anus. is just inside where the shaft goes into my body, where there is lots of soft scrotum skin. When I first noticed it I thought it was a cist and foolishly squeezed it very hard thinking I could burst it. I could tell it was there with a slight soreness for some weeks afterwards, then the soreness went away. It feels mainly detached from the penis shaft, but perhaps connected on the shaft side by a blood supply? I went to the doctor but she just couldn't find it, and told me to keep an eye. It's easier to feel when I'm aroused. A year later, I recently remembered it and had a feel and a squeeze, again. It seems the same size and after squeezing I have the same soreness. Any idea what it could be?