An Ulcer

1. (pathology) An open sore of the skin, eyes or mucous membrane, often caused by an initial abrasion and generally maintained by an inflammation and/or an infection. https://en.wikipedia.org/wiki/Ulcer_(dermatology) Genital ulcer - Wikipedia Mouth ulcer - Wikipedia Corneal ulcer - Wikipedia
2. (pathology) Peptic ulcer. https://en.wikipedia.org/wiki/Peptic_ulcer_disease
3. (figuratively) Anything that festers and corrupts like an open sore; a vice in character.