Android Developer Dashboard national/regional version
You could implement Google Analytics ( https://www.google.com.br/analytics/ ) on your app. There you can find all kinds of statistics, including country specific data.
Here is how to implement Analytics on you Android App: https://developers.google.com/analytics/devguides/collection/android/
It would be awesome if we had this from Google. There are a couple of sites/blogs that occasionally post info that can give you an idea. Device Atlas uses "mobile web data" - who knows what that means exactly but their numbers seem reasonable.
https://deviceatlas.com/blog/android-versions-market-share-2017
You can replace the "2017" with "2016" to get last year's report. Maybe they will have more in the future.