I was managed to install vikunja from docker compose. I am looking for to configure SSL for the vikunja url. How can I configure ssl? what changes do I need to do in ninx.conf file and docker compose file to make SSL work.
The first things you’ll need is to get some certificates. You can self-generate those but that will lead to browsers questioning the validity of the certificate every time you visit unless you also add an exception in every browser.
So most people use free certificates from Lets Encrypt - there are multiple ways to implement that depending on which OS you’re running on. Lets Encrypt’s own tool is called Certbot.
Once you have Certbot generating certs you need to have nginx configured to use them. Certbot will automatically configure nginx if it’s installed on the server - but if you’re running nginx in a docker it will be isolated from Certbot. And things get more complicated…and something I have no experience of (I’m using Traefik and LE wildcard certs via DNS challenge).
Look into using a reverse proxy. Caddy or Traefik is popular choices.
@adrinux summarized it pretty well 
I’m using traefik and that’s by far the easiest to set up. Also check out the example configuration for docker-compose in the docs about that.