Invalid Endblock tag in django

I am receiving an error message when I go to one of my pages in my Django project, as it is saying that the End-block tag is invalid (asks whether I remembered to register or load). The error looks like this:

My code for this template – (login.html) – is below:

{% extends "learning_logs/base.html" %}

{% block content %}

    {% if form.errors %}
    <p>Your username and password didn't match. Please try again.'</p>
    {% endif %}

    <form method="post" action="{% url 'users:login' %}">
    {% csrf_token %}
    {{ form.as_p }}

    <button name="sumbit">log in</button>
    <input type="hidden" name="next" value="{% extends 'learning_logs/index.html' %}" />
    </form>

{% endblock content %}  
   

I am very confused, and I am wondering whether anyone knows what the problem is?
Thanks
Milo