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certbot certonly in combination with the standalone plugin doesn't modify your webserver configuration in any way, not even to authorize the challenge. So it could not have caused anything at port 443.
Thank you for your quick response @Osiris. I tried to using Lets Encrypt with Nginx, but when I spin up my web app, it throws an error, " Error bind: address already in use" But port 443 is now open though not to my web app. Any advise will go along way
That suggests you were trying to use the standalone plugin while nginx is running. certbot also has a nginx plugin which can make use of your running nginx in most instances. Sometimes the nginx configuration is a little bit non-standard though and the certbot nginx plugin could have some issues. But even then it's probably perfectly possible to get a certificate without using the standalone plugin.