Problem with skin around the penis.

My cousin ,as he told me has a very tight skin around the penis.The case is such that everytime the skin is tracked down to the bottom of the tip of the penis,the skin is too tight.It is so tight that everytime he even looses his erection cause of the pain caused by it.So naturally he is unable to have sex.He has tried it twice but its the same story every time.Whenever he tries to insert it inside the vagina,the skin naturally tracks down to the tip of the penis,and the pain makes him loose his erection.All other activities like masturbating,which do not require to pull down the skin are absolutely fine and painless.The skin though,is so tight that it does not even track back and it takes alot of effort to even put it back to the starting position to begin with.Please suggest what can be done to get things to normal as it is also having a mental toll on him.He has no problem attaining an erection