In addition to being a little red the glans, when I touch the penis with my fingers or when I press over or on its sides I feel this little annoying pain in the center of the shaft, it is quite annoying because it happens to me even when I sit or do other movements that make my penis press against my briefs.
The absence of disorders related to urination or ejaculation, which you do not tell us, suggests that the source of pain lies precisely in the tissues of the penis. Given that to express an opinion the direct evaluation would certainly be essential, the experience leads me to think of the simplest cause, and the first thing that comes to my mind is sexual exertion. Maybe a little calm, patience and some simple painkillers can bring things in order in a few days. If this is not the case, direct specialist assessment will become indispensable.