Hi Doctor, I seem to have developed a boil like structure on my stomach on the upper part of abdomen. It was developed for more than 10 years now and size of it same i.e. there is no growth to it. There is small hair opening  at outside which when pressed foul odour brownish colour liquid/semi solid comes out. The odour is so strong so even after repeted hand wash the smell does not go away easily. I wanted to understand what is this and is it safe to keep it as is? As such i dont feel pain on pressing it. Please suggest what should be done here. Attached is the image.