Talk to Urologist on Pain While Passing Urine

I have a challa(White pimple Blister) inside my Male organ tip(Penis) if we open the tip of male organ a little bit, there is pimple or Blisters (like when we use to have in mouth) on the left wall of the male organ (Inside) which is causing pain as i can see it when i open it a little bit and it is causing me pain while uranting or while moving in jeans . plz suggest medince or should be i visiting any doctor