Alright I accidently had my firewall block NFBA

When I was hosting a game, it asked me to keep blocking or unblock it. I accidently clicked keep blocking. Now I cant P2P on it. Im using AVG 7.5 and i want to know how to unblock it. Any help would be appreciated.

Start > Control Panel > Windows Firewall > “Exceptions” Tab > Make sure nFBA is check-marked.