On my foreskin and top of penis there is a firmer skin area?

Get evaluated.: The skin of the penis can be affected by any of the common conditions that affect any other part of the skin. Things to worry about when there is a firm or abnormal feeling area can be of infectious, inflammatory, or very rarely, cancerous in nature. A quick check by a specialist should give you a diagnosis, and anything of suspicion should be biopsied.

No way to know.: This sounds as if it could be significant depending on age and circumstance. I would recommend you see your pcp, dermatologist or urologist.