Nuke generally gives you an undo history that extends back to the first action of the application’s current session.
Select Edit > Undo (or press Ctrl/Cmd+Z). Repeat as necessary.
Select Edit > Redo (or press Ctrl/Cmd+Y). Repeat as necessary.
Click the Undo arrow button in the properties panel.
Click the Redo arrow button in the properties panel.
Click the Revert button .
OR
Right-click on the properties panel and select Revert knobs.
Right-click on the properties panel and select Set knobs to default.