n. 25B6; verb
his deep wound festered : SUPPURATE, become septic, form pus, weep; Medicine maturate, be purulent; archaic rankle.
rubbish festered : ROT, moulder, decay, decompose, putrefy, go bad/off, spoil, deteriorate.
their resentment festered : RANKLE, eat/gnaw away at one's mind, brew, smoulder.