as per your symptoms it seem to my belief you are mingling two different problem, must be a chance you have abscess
right down under your question tooth which will require a ROOT CANAL TREATMENT
your other problem which is a mark kind could be some insect bite or allergy
, but for exact diagnosis could only be made with physical examination to rule out the possibility causing the discoloration of the skin.
see a dentist
soon , delay your appointment until you can bear the pain.
start with warm saline (half cup luke warm water+ half tbs salt)rinses at night , it helps in drainage
of pus in the abscess .