To close incognito tab from your phone you can use following steps:
- If you have Android 5.0 (Lollipop) or later, swipe from the top and touch Chrome: Close all incognito windows.
- If you have an earlier version of Android, go to the corner of each of your incognito windows and touch the X.
For iPhone or iPad:
To close incognito mode, go to the corner of each of your incognito windows and touch the X.
For reference you can visit: Browse in private with incognito mode.