Nginx 502 Bad Gateway error on EC2 Instance with dango - django

Question

I'm using Nginx in my EC2 instance to attach my domain from route 53 with my Django app which is running in a docker container, it was working totally fine but as I move my database to the RDS and after moving it my application is not working there, Nginx is throwing me the error attached below:
2022/04/07 21:15:40 [error] 9#9: *3 connect() failed (111: Connection refused) while connecting to upstream, client: 202.47.34.198, server: , request: "GET /favicon.ico HTTP/1.1", upstream: "uwsgi://172.20.0.3:9000", host: "sub.domain.com", referrer: "http://sub.domain.com/"
/etc/nginx/sites-available/default
server {
root /var/www/html;
# Add index.php to the list if you are using PHP
index index.html index.htm index.nginx-debian.html;
server_name sub.domain.com;
location / {
proxy_pass http://localhost:80;
proxy_set_header Host $host;
proxy_set_header X-Forwarded-Proto $scheme;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
client_max_body_size 100M;
}
listen [::]:443 ssl ipv6only=on; # managed by Certbot
listen 443 ssl; # managed by Certbot
ssl_certificate /etc/letsencrypt/live/sub.domain.com/fullchain.pem; # managed by Certbot
ssl_certificate_key /etc/letsencrypt/live/sub.domain.com/privkey.pem; # managed by Certbot
include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}
server {
if ($host = sub.domain.com) {
return 301 https://$host$request_uri;
} # managed by Certbot
listen 8080 default_server;
listen [::]:8080 default_server;
server_name sub.domain.com;
return 404; # managed by Certbot
}
netstat -tulpn | grep LISTEN
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 127.0.0.1:40743 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:8080 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:443 0.0.0.0:* LISTEN -
tcp6 0 0 :::8080 :::* LISTEN -
tcp6 0 0 :::80 :::* LISTEN -
tcp6 0 0 :::22 :::* LISTEN -
tcp6 0 0 :::443 :::* LISTEN -