Fester
v.intr.
To generate pus; suppurate.
To form an ulcer.
To undergo decay; rot.
To be or become an increasing source of irritation or poisoning; rankle: bitterness that festered and grew.
To be subject to or exist in a condition of decline: allowed the once beautiful park to fester.
v.tr. To infect, inflame, or corrupt.
n. A small festering sore or ulcer; a pustule.