Hello,
What your son is having is a concealed or webbed penis. A concealed penis is a normal-sized penis that lays hidden in the pubic fat pad and is common in some infants. It can be easily exposed by gently pulling on it or by pressing down on the surrounding fat pad but if the symptoms are severe then surgery may be required. Please consult a urologist in that case.
I hope it helps. Take care and regards.
my nephew has the same problem he is still little and his pediatrion told us just to push the skin back when bathing and changing his diapers and if there is really no change when he gets a little older they are talking about doing his circumcesion again becouse it didnt heal rite