What Causes A Lump On The Left Of The Belly Button?

Hi,

I have this penny sized lump right under my skin, to the left of my belly button. At first I thought it was a pimple, but I noticed it hasnt gone away for about 2 weeks now. After I showered, I pressed on it, and it feels like it's a little to deep to be a pimple. i tried to pop it, and some pus and blood came out, but a few hours later the lump still feels stiff and deep. hasnt gone down since i tried to pop it. and now its a little sore when i touch it. what could this be? the pus is a light brown color. not dark, light with a little red. it looks similiar to the thousand island dressing kind of color... (gross, i know) its red in appearance, hasnt changed color. please let me know. thank you in advance