While your DNAR are staked by nominating a validator, they are 'locked' (bonded). You can receive new DNAR in your account but you cannot stake as validator or transfer DOT away from your account. You can un-nominate at any time to stop staking your funds. Keep in mind that the un-nomination is effective in the next era, and that un-nominating does not automatically unbond your funds. There is an unbonding period of 28 days before bonded funds can be transferred.