No. Any messages sent to you while a person was blocked are blocked by the system and will not be delivered to your inbox after you unblock them. They essentially disappear into the void.
Here’s a clear, step-by-step guide on how to unblock a friend on Facebook, along with important things to know before you do. how unblock facebook friend
: Click Privacy in the left-hand menu, then select Blocking . Edit Blocked Users : In the Block users section, click Edit . click Edit .