According to the FEW, the secondary sense of ‘bruise’ is attested in Latin from the third century in pustella, ultimately a variant form of postula. The DMLBS does not include this word, variant or sense.
s.
1pathol.med.pustule, boil, raised lesion of the skin that contains pus:
(
s.xiii2/4; MS: s.xiii3/4
)
Et por la repression des pustules confise om creie ou terre de gleise et de vin egre et fac[e] om emplastre
i 249
2pathol.med.bruise, contusion of the skin caused by a blow:
(
s.xiii1/4; MS: s.xiiim
)
Dist Reneward: ‘Receu avez pusteles, Ne sai des altres, mais vus morst la feste’
3438
pustule (s.xiii1/4)