Please note that just deleting the number will not delete the account. The steps linked above needs to be followed for this issue to be resolved.
When submitting the confirmation code, the message "Finish Registration Error" appears
When there are multiple registration attempts, Facebook will interpret these actions as Spam and temporarily block the number.
Facebook does not permit multiple registration attempts in quick succession. Please allow a 2 min timeout between registration attempts. After 3 successive registration attempts, Facebook will initiate a 2 hour timeout period.
This means that you will need to wait at least 2 hours to try again.