Google Play Store is not the only place to get Android applications and games. You can apps and games in apk format that not available in Play Store on Internet. By default, you can’t install them on your Google Nexus 4. Google blocks it because some of these apk might contain malware especially those pirated apps like warez. And they might breaks security on Nexus 4 by stealing your personal information or load advertisements as part of push notification. Therefore, only install applications and games apk from well-known and safe sources.