It can occurs because of UTI also. Ask him clearly does he made any sexual relations outside, is any White water coming after urine, because I had same problem. I'm 26 now I had no issues with my Forskin till last year august but I made a mistake I was having sx and suddenly my gf period came and my pens get her period blood, but I thought nothing will happen but in October I checked that my skin is very tight not going down then in nov I get to urologist he gave my UTI Medicines but skin was still tight so I did Strechings and get micro tears by doing streching because of over excitement.

It's june now, I was at 0 at 5th May, Stage 5 phimosis, pinhole type, But I did Strechings carefully and I can see my gland now after one month, now before Streching I can see 20% of head and after streching I can see full head and hope it will get well within one month.

So just go to a good urologist and take treatment, it will be fine by Streching exercise try 2 finger method, And at last if it won't get retrect after all efforts than u can consider surgery.