How To Cure Acne On Face?

Hi, I have a big "pimple", but you can't really call it a pimple anymore. It's on my nose and it has been there for about a year. It started out as a normal pimple, but it became inflamed when someone elbowed me on the nose. My doctor prescribed me with Altabax, which is a Retapamulin that treats impetigo. The pimple calmed down after a few weeks, but there was still a mark on my face. About a few weeks ago, it grew back, and now there is a grayish, redish bulging spot on my nose. It does not itch, however. My question is: What is the most effective strategy to remove something like this? Thanks!