Okay so what do i do about those litte surviving flies?

Okay me an mom found a tub of old potatoes in the pantry. thats where the little flies were coming from. we cleaned the pantry. and the kitchen where the pantry is. theres still 15 maybe 25 little flies still flying around. do i have to spend my time killing each one, one by one? or will they just die? please help, thanks