However, if black pushes in at 1, white must defend their territory at 2.
This puts black’s stone at 1 in atari (in danger of being captured), so black must defend at 3.
Once black has defended, black is threatening to capture white’s stone at 2 so white defends at 4, making a tiger’s mouth.
If you can’t see why white must defend after black 3, feel free to try find the variation on your board.
Now the position is settled and white’s bottom-left corner only has 7 points. White has lost 2 points because black has pushed in at 1.
Because black has the ability to reduce white’s points with 1, black should not end the game yet.