probably you have phimosis
as your penis head not coming out.
it may due to many reasons like infection of the foreskin or glans
/from childhood etc.
depending upon the causes and how long it is present there the treatment will deffer.
you can try to pull it back daily after giving some lubricating ointment/gel.
usualy it is corrected by surgery.
its an easy and safe method.
so please consult a surgeon.
after examination of that part he will guide you properly.