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The white hard substance is actually the cause of the problem. It is called smegma and is formed of dead cells, bacteria and secretions. It collects under the foreskin if you do not keep good genital hygiene. You should daily retract your foreskin and wash it thoroughly. If you do not do it, the smegma will keep on collecting and cause inflammation and fibrosis of the foreskin and as a result, it becomes inflexible and inelastic. Now you should better get rid of the foreskin by surgically removing it. That will not only keep your penis clean but also reduce the risk of sexually transmitted diseases and cancer of the penis.