I had a very tight foreskin when young.
When erect and uncovered, I could not pull the foreskin back up, it was that tightly taut under the coronal ridge. I'd have to wait until the erection faded, which didn't always happen after ejaculation. From time to time I really had to make an effort to get it pulled back up while my gf/wife looked on in either amazement or puzzlement. Not sure what she thought … ha ha
In any case, around my forties, I started to make a conscious and deliberate effort to stretch and widen the opening. Essentially, while by myself, I would apply any kind of cream, oil or lotion I could get my hands on, apply it liberally and then start pulling the foreskin up and down. I would also insert small objects, like two wooden popsicle sticks or small tea spoons under the foreskin, each opposed to each other and then pull the foreskin pen as far as I could, sort of like using a homemade hemostat I guess.
It was a slow process, but it did work quite well and now I can retract the foreskin in a jiffy with no discomfort and keep it retracted (with the aid of clasps and frenulum rings) for hours on end if I wish. And I often do.
Another anatomy change is due to my pneumonectomy, which caused the ribs on my right side to grow outwards a bit, causing a bit of noticeable asymmetry.