You have two options: 

1. Hit the "save" button which saves the original photo but with your edits applied to it. If you try to edit this again you'll see you can undo all the edits you made. 

2. Go to settings and hit "save as copy" this saves a copy of the photo with only the final version available. 

Alternatively, you can screenshot your edited photo if you want to be double sure and to strip some metadata.