You can take any action as long as you are the administrator of the blocked group. If this is true and you are the administrator:

1. Read the License Agreement and the Group content requirements carefully as well as the item of the rules you have violated, which resulted in your group being blocked.
2. Remove all content violating the rules (topics, photos, links) from your group.
3. Only then it makes sense to contact the Customer Support Team and discuss the possibility of unblocking your group.

Please note that the final decision is made by the website's Administration. It's better to prevent violations in the group than try to unblock it later!