Error: Invalid assignment of property or key 'text' with value of type 'String' on a base object of type 'null instance'.

Godot Version

4.3

Question

This is my script :

extends CharacterBody2D

@onready var puzle2 = preload("res://Scenes/Puzzle2.tscn")
@onready var label: Label = $Label
@onready var Score: Label = $Label2
@export var speed = 2
var jump_force = -400
var gravity = 500
var move_distance = 3
var random
var score = 0
var my_velocity = Vector2()

func _pick_new_key():
	random = randi_range(1, 5)

func _ready():
	my_velocity.x = speed
	_pick_new_key()

func _physics_process(delta):
	Score.text = "score:" + str(score)

	if random == 1:
		label.text = "Press D"
	if random == 2:
		label.text = "Press A"
	if random == 3:
		label.text = "Press space"
	if random == 4:
		label.text = "Press W"
	if random == 5:
		label.text = "Press F"

	if random == 1 and Input.is_action_pressed("Button1"):
		_pick_new_key()
		score += 100
	if random == 2 and Input.is_action_pressed("Button2"):
		_pick_new_key()
		score += 100
	if random == 3 and Input.is_action_pressed("Button3"):
		_pick_new_key()
		score += 100
	if random == 4 and Input.is_action_pressed("Button4"):
		_pick_new_key()
		score += 100
	if random == 5 and Input.is_action_pressed("Button5"):
		_pick_new_key()
		score += 100

	if is_on_floor() and Input.is_action_pressed("ui_up"):
		velocity.y = jump_force
		move_and_slide()

	if not is_on_floor():
		velocity.y += gravity * delta
	else:
		my_velocity.y = 0
	position.x += speed  
	move_and_slide()

and I am getting the error: Invalid assignment of property or key ‘text’ with value of type ‘String’ on a base object of type ‘null instance’.
{88D52B39-8F68-482F-8F57-382C75C0C2AC}
this is my scene tree

Which line gives the error?

I dont know it just gives this error when I run the game