The technical way is to use Android's App Licensing feature to protect paid applications. However, this is complicated and involves a lot of technical knowledge, you either implement this through Android Studio, Cordova or through a Cordova Plugin. This involves native coding and optionally a validation server, advanced for Construct 3 users, you have to plan in advance if this is worth investing time into.
The easiest workaround is to change your application from a paid application model to an in-app billing model. This means to provide a free/demo version first, then letting them pay the full version of the game in the application rather than from the Play Store.
However, even in-app billing models also have its own share of difficulties as well. You also need to have a validation server as well to be full-proof, though this is easier to do now because of available features.
I hope that helps.
After thinking long and hard, I came up with a relatively simple idea.
I can use the IAP Purshase plugin to do this check.
This plugin DOES NOT connect with Google if the app is not installed by the Play Store, so I thought of registering any product for sale in the app, this plugin will try to check the available products and will not succeed if it is not installed by the Play Store , this error will indicate that the app was not purchased and I can deny access.
If the plugin receives information about the products registered for sale, then the game was purchased correctly and I can grant access without requiring any additional purchase.
Theoretically functional, I will test today and tell you if it worked.