focus

That white stuff is called smegma. Its a thick, cheese-textured substance that normally forms under the foreskin, and is usually found on the head, and just behind the ridge of the head when pulling the foreskin back. It builds up over time, so if you haven't pulled your foreskin back before, you'll probably have a lot of it. You should retract your foreskin everyday in the shower and quickly wash/rinse the area with the foreskin retracted to keep it from building up.

Smegma is made up of dead skin cells from the head and inner foreskin, mixed with some skin oils, and a bit of urine and sometimes semen. A little bit of smegma is normal and healthy, as it helps lubricate the foreskin so it glides over the head smoothly. But if it is allowed to build up and get old, it can smell bad, and possibly cause irritation.

Since you have a large build up of it as you just retracted your foreskin for the first time, regular soap and water may not work getting rid of it. Try using a bit of baby oil on the smegma. The baby oil acts like a solvent to help loosen the stuff up, without harming the sensitive skin of the foreskin and head. It will take some work to get it all cleaned up, but from now on, as long as you keep retracting your foreskin and cleaning under there at least several times a week, it will be much easier to clean.