useNavigation
useNavigation is a hook which gives access to navigation object. It's useful when you cannot pass the navigation prop into the component directly, or don't want to pass it in case of a deeply nested child.
useNavigation() returns the navigation prop of the screen it's inside.
Example
import * as React from 'react';
import { Button } from 'react-native';
import { useNavigation } from '@react-navigation/native';
function MyBackButton() {
  const navigation = useNavigation();
  return (
    <Button
      title="Back"
      onPress={() => {
        navigation.goBack();
      }}
    />
  );
}
See the documentation for the navigation prop for more info.
Using with class component
You can wrap your class component in a function component to use the hook:
class MyBackButton extends React.Component {
  render() {
    // Get it from props
    const { navigation } = this.props;
  }
}
// Wrap and export
export default function (props) {
  const navigation = useNavigation();
  return <MyBackButton {...props} navigation={navigation} />;
}