error when printing the data of a logged in user ..!

Sorry for the inconvenience, but I have a great doubt, I get an error when showing the data of the logged in user, the strange thing is that if you allow me to enter the moment I enter the username and password.

I have a file login.php .

<?php
  require_once("clase/conexion.php");
  if(
    isset($_REQUEST["user"]) &&
    isset($_REQUEST["pass"])
    ){

    $query = $mysqli->query("
      SELECT * FROM admin 
        WHERE usuario = '".$_REQUEST["user"]."'AND 
              password = '".$_REQUEST["pass"]."'
      ");
    $con = $query->fetch_assoc();

    if(
      $_REQUEST["user"] == $con["usuario"] &&
      $_REQUEST["pass"] == $con["password"]
      ){
        session_start();
        $_SESSION["user"] = $con["usuario"];
        $_SESSION["pass"] = $con["password"];

        header("Location: inicio.php");
        }
    }
?>

and a view where I print the name of the user that is logged in home.php

<?php echo $_SESSION["usuario"]; ?>

and I get this error, telling me that in the view where I print the user's name is undefined which would be $ _ SESSION ["user"] .

Undefined index: user in C: \ wamp64 \ www ..