What Causes Pain In Foreskin While Retracting It Back?

hi my age is 20 yrs my foreskin on my penis pains me when i retract,and i never tried to completely retract n left it likewise but when i was bathing yesterday i could completely retract the skin with some pain n saw white nodules over my glans borders n saw white foul discharge i feel so feared when i googled it n saw that it may be related to penile cancers also i have same pain there all the time please give me a suggestion of what to do???