Sounds like smegma. You need to pull back the foreskin each day in the shower and rinse all secrections off with plain, clean water. If yo have never done this and there is a build up then see my stretching instructions at the top of the mens health board. There's a section on removing smegma build up.
It could also be dried semen or pre-ejaculate if you haven't washed your penis after you last ejaculated or became aroused enough to release pre-ejaculate. You could also have release semen during a wet dream without realizing it.