Next, select Text Replacement, tap the add sign and enter "i" in the Phrase box and "I" in the Shortcut box, and hit Save.
Voila! That should enable you to once again communicate freely in first person, and banish the autocorrect error.
UPDATE, November 9: Apple just unleashed an update (iOS 11.1.1) which includes a fix that patches this specific issue. To update, launch the Settings app and head to General > Software Update.