How To Cure A Big White Pimple On Penis Which Causes Pain?

Hello , I have a big white pimple on my penis , it doesn't get bigger or smaller and it never hurts when i touch it. It's been there for over a year and a half now and i don't know what to do. I think it's really awkward/embarrassing if i went to see a doctor. so can anyone tell me anything about it ? is it serious ? and how could i get rid of it ?