Hungry flies bite sore.

Literally, the image suggests that hungry flies bite more painfully: hunger is presented as an immediate pressure that makes even a small nuisance more sharply felt.

Figuratively, the saying warns that deprivation may intensify irritation, pressure, or aggression. It invites attention to hardship behind harsh behavior without treating that hardship as an excuse for the harm done.

Use it as a concise, reflective observation that want or scarcity can make conduct more forceful or hurtful. It is better as a warning about pressures surrounding behavior than as a precise explanation of any one person’s actions or an endorsement of their harshness.