Turn on Prefab with Keycode issue

Hello, I have this code where when I press E it turns on a prefab, but issue is when I walk away from the collider an press E anytime it turns on the prefab. So if I walk upto the box an decide not to press E then later on if I press E it turns on a prefab anyway. How do I fix it so if I collide an press E then it turns on Prefab and if I walk way from the box then it wont turn on with E button.

 using UnityEngine;
 using System.Collections;
 
 public class Turn_On_PREFAB : MonoBehaviour {
     public GameObject Prefabtoactivate;
     public GameObject locationtospawn;
     bool pressed;
     bool entered;
     // Use this for initialization
     void Start () {
         pressed = false;
         entered = false;
         Prefabtoactivate.SetActive (false);
     }
 
     void OnTriggerEnter(Collider other)
     {
                 entered = true;
         }                
     void HIT (){
         Debug.Log ("HIT");
         Prefabtoactivate.SetActive (true);
     }    
     void Update () {
 
         if (Input.GetKey (KeyCode.JoystickButton0) || (Input.GetKey(KeyCode.E)) && entered == true) {
         
             HIT();
     }}
 }