From the Inspection page, select the photo you want to reassign to a different question or category by tapping on it.
Select the drop-down at the top of the app.
Click the correct category or question for the photo from the list of options.
The dropdown should now show the chosen question/category.
If you go back to the Inspection screen (by clicking the Home button at the top left of the app), you should see the photo in the correct location.
Note: if there is a photo limit to one of the questions, and it has already been reached, a photo cannot be moved to that question until there is room for it.