Google My Business posted on Twitter that businesses owners can use now the Google Maps iOS app to edit their business profiles. This is without using the Google My Business app or web site.
The announcement reads "Owners and managers of businesses can edit the information on their Business Profiles directly from the Google Maps iOS app. This makes it easier for verified owners to manage their Business Profile. Learn how you can edit your info or add photos directly from your Business Profile on Google Maps iOS."
I personally do not see this option yet but maybe it isn't fully rolled out yet?
Forum discussion at Twitter.