On the lower left side of my mouth, behind my last molar (I had my wisdom teeth removed years ago) there is a swollen spot on my  gum.  There is only mild pain when I touch it, except for one area that has a more acute pain.  That area is darker than the rest of the gum (something like a mix of purple and black).  When I wipe the dark area with the tissue and smell the tissue, I can smell the stink of plaque.  Is this swelling something that will go down naturally (if so, how can I help it along?), or should I see a doctor or get a prescription for antibiotics?