No. Messages sent during the block period are permanently lost and will not deliver retroactively.
The process for unblocking on Android is generally standard but may vary slightly by manufacturer (e.g., Samsung or Pixel):
Complete Guide to Unblocking a Phone Number If you previously blocked a contact, telemarketer, or spammer, you can easily reverse this setting. The process varies slightly depending on your smartphone operating system, carrier, or landline provider. Unblocking Numbers on iPhone (iOS)