Buried Penis

My LO is circumcised and once he hit 3 months his penis head has started to sink into his skin folds. I have to pop it out during nappy changes.

Has anyone else had this happen to their son?

The surgeon told me it could happen and that he should grow out of it but I am just wondering if it is a common thing and if any mums had it happen to their kids and if it has gotten better once they started walking etc!