There are a couple of options. The simplest to deal with is to delete all prior season's games from the system. See the linked article for more info.
To completely delete one or more games without deleting everything:
- You'll need to enter a special mode that is normally hidden to keep you from accidentally using functions that may have unintended consequences.
- Under the "Account" Menu, select Advanced Options...
- On the page that loads, click on "Enable Advanced Game Functions":
- Go to the games page and use the filter to search for all your older games
- Select an appropriate date range
- Select "Include Canceled"
- Optionally increase the number of games to list on one page
- Click the check boxes of the ones you want to delete (if desired, use the "Check All" button to get all of them at once)
- Click the red-outlined black X (at the right end of the action buttons)
All of the selected games will be fully and permanently deleted. You will NOT have to option to restore games deleted in this manner.