/ˈfestər/
fes·ter
BrE /ˈfestə(r)/
NAmE /ˈfestər/
[I] (of a wound or cut)
to become badly infected
festering sores/wounds
Fengge sprayed 75 alcohol on the wound afterward, the wound worsened, got infected and festered, the leg is already ruined!
[I] (of bad feelings or thoughts)
to become much worse because you do not deal with them successfully