Security with android

Hello everyone, i’m working on an app in wich i will need a LogIn system, and the players will be able to send scores, for that i’ll use a SQL connection.

However, i’m aware that i need some security method, if i don’t want people injecting on my database.

Does someone have any recommendation on how to do that, or what should i search for?

I’m programing my app on C#.

it happens you really need to do this stuff