What Causes Discolouration Of Penis Foreskin?

Hi Doctor, I have discoloration on the outside of the foreskin. its about the size of a dime (10 cents coin) and I had it for a long time; more than a year. Lately, I noticed that is is spreading towards the rim of the foreskin. By the way, I am not circumsized. Sometimes, before I take a shower, I notice some whitish , cream like presence, odorless, on the inside of my foreskin. I have no pain, no itching, only the discoloration. Should I be concerned? Thank you.