The same thing happened to my son at his 4 month checkup, he's 9 months now. The ped's reasonsing was that they pull back the foreskin when doing a circ, so what's the difference? Astounding ignorance. Anyway, for probably a few days afterward the foreskin was irritated, with very small red lines on the end. After these went away, he hasn't had any further issues - except that the foreskin tightened up again, and I was concerned about adhesions. About six weeks ago, I noticed when bathing him that his foreskin appeared much looser and when he played with it (something he just naturally seems to love doing!), he was at least partially retractable, possibly as a result of him stretching it himself, or natural separation, or both.
I was very upset and concerned after the retraction, and just like you, I was looking for answers about what might happen in the future. I've done a great deal of reading here from people who have been through the same issue, and the consistent message seems to be: a one time retraction is very unlikely to lead to problems in the future. It's forced retraction happening over and over again that can possibly lead to problems.
If you can, do let us know how your son is doing.
Best wishes,
Peter