First, make sure you use HTTPS when fetching the metadata from Open edX. Otherwise it will use http in the metadata.
Second, when you view the metadata, if you are accessing the metadata over HTTPS but it contains an http URL, then django is mis-configured. Whatever proxy server is handling your HTTPS connection should be passing some headers to Django to indicate that the request was HTTPS, but Django isn’t seeing those headers. Check the SECURE_PROXY_SSL_HEADER setting, which should be what you need to change to fix it.