済まさなければ

if [someone] doesn't finish, if [someone] doesn't get done

→ 済ます
済まさ finish, complete + なければ Negative conditional (“if not”)
verb · conditional Rare #41,873
if [someone] doesn't finish, if [someone] doesn't get done
JA: 宿題を済まさなければ、遊びに行けません。
EN: If I don't finish my homework, I can't go play.
Conjugation of 済ます
Conditional
済まさなければ

戦時中はしばしば砂糖無しで済まさなければならなかった

During the war, we often had to make do without sugar.

もしお金がないのならなしで済まさなければならない

If you don't have any money, you'll have to make do without it.

私たちは今年は休日なしで済まさなければならないようだ

It looks like we'll have to get by without a vacation this year.