Artur Nuraev

В общем решил так:

location /main-back/ {
    proxy_pass          http://main-back:80/main-back/;
    rewrite /main-back/(.*) /$1 break;
    proxy_set_header    Host $host;
    proxy_set_header    X-Real-IP $remote_addr;
    proxy_set_header    X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header    X-Forwarded-Proto $scheme;
    location /main-back/docs {
      rewrite /main-back/(.*) /main-back/$1 break;
      proxy_pass          http://main-back:80/main-back/docs;
    }
  }