How does one's foreskin grow back, and what does one do when it does? Is there anything one can do to prevent it from growing back in the future?
5It doesn't grow back– יהושע קDec 4, 2021 at 16:46
1I suspect this question to be a troll. Regardless: the foreskin does not grow back after circumcision.– ezraDec 5, 2021 at 6:18
It sometimes happen by children who were circumcised for medical reasons that too much skin is left over so they need a circumcision revision.
Such a thing almost never happens by milah. Let alone one done on an adult convert. If it does happen then the person may need a new circumcision (for maaris ayin purposes. See Shulchan Aruch YD 264:6). However it is not something rushed into. No responsible Mohel is going to do it without the person consulting and getting clearance from a urologist. Nor will he do without the presence and oversight of a competent medical professional at the time.
The only case I know of an adult who had a regrown foreskin the consensus was that another circumcision would be too dangerous so it was not done (as told to me by the two mohelim involved in the story)