Detect trigger. Destroy the GameObject if the player clicks mouse button.

public class StoneNode : MonoBehaviour {

    // Number of hits it takes to harvest the node.
    public int stoneHitsRequired = 5;
    public int clickNum = 0;
    
	// Use this for initialization
	void Start () {
        
    }
	
	// Update is called once per frame
	void Update () {

	}

    void OnTriggerEnter(Collider SphereCollider)
    {
        if (Input.GetMouseButtonDown(0))
        {
            clickNum++;
            if (clickNum >= stoneHitsRequired)
            {
                Destroy(gameObject);
                clickNum = 0;
            }
        }
    }
    void OnTriggerExit(Collider SphereCollider)
    {
        clickNum = 0;
    }
}

I figured it out. Here are my changes:`public class StoneNode : MonoBehaviour {

// Number of hits it takes to harvest the node.
public int stoneHitsRequired = 5;
public int clickNum = 0;

// 1 if in trigger 0 if not
public int inoutTrigger = 0;

// Use this for initialization
void Start () {
    
}

// Update is called once per frame
void Update () {
    if (inoutTrigger == 1)
    {
        if (Input.GetMouseButtonDown(0))
        {
            clickNum++;
            if (clickNum >= stoneHitsRequired)
            {
                Destroy(gameObject);
                clickNum = 0;
            }
        }
    }
    if (inoutTrigger == 0)
    {
        clickNum = 0;
    }
}

void OnTriggerEnter(Collider SphereCollider)
{
    inoutTrigger = 1;
}
void OnTriggerExit(Collider SphereCollider)
{
    inoutTrigger = 0;
}

}`