Most likely an ingrown hair. All but the deepest layers of suture are disolving and are gone in six weeks. I use 3-0 silk to ligate superficial veins but I have never seen one of these spit in a clean case.
Soap and water to keep it clean and dry are generally all that is needed for resolution. Your skin will eventually spit the offending hair debris. If the area of redness is wide you may need to see a doctor to make sure it is not something more serious requiring antibiotics and or I&D. Do not pick or poke it with a sharp instrument. If you are diabetic the cause for concern is greater and you should consult your physician