Acne on the navel

So in the beggining I thought it was just a pimple like infection on my navel. But after a few days it seems to have been growing bigger and bigger. There is a foul odor coming out of my navel and it is now causing minimal disconfort, which was not the case when it began.The area around it is now swollen and I hope that it might go away on it's own, but if it does not I will definetly have to see a doctor. I am just wondering what your opinion is on this infection, and how long should I wait to see a doctor. Thanks for your help.