Could someone help me fix this error (CS0122)?

Here is the script in question that is causing the problem;(PotionJump.cs(19,50)
error:‘CharacBehavior.isGrounded’ is inaccessible due to its protection level:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PotionJump : MonoBehaviour {

	// Use this for initialization
	void Start () {
	// Update is called once per frame
	void Update () {

	void OnTriggerEnter2D(Collider2D col){
			col.gameObject.GetComponent<CharacBehavior>().isGrounded = false;
			Rigidbody2D rb = col.gameObject.GetComponent<Rigidbody2D>();
			Vector3 velo = rb.velocity;
			rb.velocity += new Vector2(0, -velo.y);
			rb.velocity += new Vector2(0, 25);

If it’s inaccessible due to protection level, it means the GetComponent you are trying to access in the script CharacBehavior is not set to public. So you either have the bool isGrounded not set as public, or the script itself is not public (or might not be setup right). My guess is you didn’t make the bool public.