When Piggy Bank’s spin limit is over, it will stop collection spins until you purchase it. And, after buying Piggy Bank, you can break it.
You can check Piggy Bank’s spin limit by tapping your Piggy Bank.
In simple words, you can not break Piggy Bank without purchasing it. To break Piggy Bank in Coin Master, you need to buy it, when Piggy Bank is full by it’s spin limit.