I accidentally blocked or allowed an application! How to reverse this? [v3-5]

Comodo Internet Security - CIS Firewall FAQ - CIS
1

Q:
I blocked an application, how can I undo this?

A:
For CIS versions < 5.x:
Navigate to Firewall>>>Advanced>>>Network Security Policy, Application Tab

From CIS version 5.x:
Navigate to Firewall>>>Network Security Policy, Application Tab

Find and remove that particular application/process you Denied.
You can also Edit to Block the application, etc.