If you send unbond delegation transaction:
simd tx staking unbond [validator-addr] [amount] [flags]
Here is what happens when you complete unbond transaction: [State Transitions]
If the unbonding period has not yet passed, and you urgently need to delegate tokens to the validator, you shoud send cancel unbond delegation:
simd tx staking cancel-unbond [validator-addr] [amount] [creation-height]