Depending on their privacy settings, you may also be able to see things like their status updates, comments, likes and tags on Facebook.
Bear in mind that when you block someone, they’ll no longer be able to contact you (ex: send you messages, call you) on Messenger or on Facebook chat. See: How to Locate Archived Conversation in Messenger
How to Unblock People in Messenger
If you’ve blocked messages from someone, you can unblock them later. To unblock someone on Messenger:
iPhone and iPad:
1. From Home, tap your profile picture in the top left corner.
2. Tap People and then tap Blocked.
3. Tap the name of the person you want to unblock.
4. Tap next to Block Messages to unblock them.
Read: Steps on How to Delete or Clear Notifications on Facebook
Android:
1. Form Home, tap your profile picture in the top right corner.
2. Scroll down and tap People.
3. Tap Blocked people.
4. Tap Unblock next to the name of the person you want to unblock.
5. Tap Unblock on Messenger.