There is very little science on this effect, although most have (had) this blister-like swelling. My explanation is that foreskin is also muscular. When you cover your glans, the skin contracts slowly to form the prepuce. Must be some sort of slow muscle layer doing that. When you retract it can't, and initially objects by swelling. Often, the part that takes most of the time retracting permanently is to loosen up that section of the skin. It is like a rubber band. On mine still slightly visible when retracted. But at least no more swelling. I had a lot of those in the past. My skin is thicker than average and thus more muscular-like. The rubber band also still keeps pushing the skin towards the glans.
I think the swelling helps the skin adjust to the new position. Later it will wrinkle more, and more all the way down. My own first worries were that the swellings would just grow me more skin to keep back. Thinking lengthwise, not girth-wise. Yet over time, the opposite happened. The wider the rubber band got, the shorter the skin now seems to be.
I think it is a very natural process. With it's own alarm bell. When too much, it would sting in a clearly unpleasant way. Time to temporarily keep forward and let the swelling subside. In the past, I had some skin instability on my covered glans. Balanitis or the other one, white itchy spots. Now no longer. It is as likely now to have a balanitis on my glans as it is likely to have balanitis on my left pinky finger or my right ear lobe. Yet do not take this as medical advice. Just sharing experience and research.