Yes, my blog is a static blog deployed to gitlab servers automatically after every push. In gitlab settings, there is a page to add the .pem file manually
I just ran the following command and uploaded the acme challenge file as instructed and it renewed the certifcate successfully
sudo certbot certonly -a manual -d animesh.blog
Cert is due for renewal, auto-renewing...
Renewing an existing certificate
...
To non-interactively renew *all* of your certificates, run
"certbot renew"
So I guess this is the only way to renew for a cert created manually. Then to paste again the .pem files in gitlab settings manually is quite inconvenient. I will have to find a way to script the authentication process.