fester
/ˈfɛstə(ɹ)/
noun
Meaning
A fistula.
A sore or an ulcer of the skin.
The condition of something that festers; a festering; a festerment.
verb
Meaning
To become septic; to become rotten.
To worsen, especially due to lack of attention.
"Deal with the problem immediately; do not let it fester."
To cause to fester or rankle.