I have a boil...?

I have had a boil for about a week. I put what they call black salve on it for 2 days and nothing happened so I cut a potatoe in half last night and left it. When I woke up and got in the shower. It busted and all this stuff came out. It was nasty. Now I have a hole in my skin. Will it close up? Will I have scarring? DoI need to cleanse my blood somehow? If so how? With what foods?