【Rails/EC2 】502 Bad Gatewayと表示される【Unicorn/Nginx】

##前提・困っていること
現在RailsアプリをAWS上にデプロイをしたいのですが、サーバー関連で詰まっています。

EC2上にUnicornとNginxを導入したのですが「502 Bad Gateway」とブラウザに表示されています。

EC2のセキュリティグループは下記になります。

ご教授いただけましたら幸いです。

Nginxの設定ファイル

upstream unicorn {
  server unix:/sample-app/src/tmp/unicorn.sock;
}

server {
  listen 80;
  server_name ☓☓☓☓☓☓☓;

  access_log /var/log/nginx/qiita_access.log;
  error_log /var/log/nginx/qiita_error.log;

  root /sample-app;

  client_max_body_size 100m;
  error_page 404 /404.html;
  error_page 500 502 503 504 /500.html;
  try_files $uri/index.html $uri @unicorn;

  location @unicorn {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $http_host;
    proxy_pass http://unicorn;
  }
}

Unicornの設定ファイル

worker_processes 4

listen File.expand_path('tmp/unicorn.sock')
pid File.expand_path('tmp/unicorn.pid')

stderr_path File.expand_path('log/unicorn.log')
stdout_path File.expand_path('log/unicorn.log')

preload_app true

before_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
    Process.kill 'QUIT', Process.pid
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!
end

after_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.establish_connection
end

##追記
unicorn.log

I, [2021-03-21T23:52:34.461522 #26347]  INFO -- : Refreshing Gem list
I, [2021-03-21T23:52:35.256972 #26347]  INFO -- : listening on addr=/home/ec2-user/game-bug-app/src/tmp/unicorn.sock fd=15
I, [2021-03-21T23:52:35.294266 #26347]  INFO -- : master process ready
I, [2021-03-21T23:52:35.329151 #26358]  INFO -- : worker=0 ready
I, [2021-03-21T23:52:35.330048 #26359]  INFO -- : worker=1 ready
I, [2021-03-21T23:52:35.334340 #26361]  INFO -- : worker=3 ready
I, [2021-03-21T23:52:35.335187 #26360]  INFO -- : worker=2 ready
bundler: failed to load command: unicorn_rails (/home/ec2-user/.rbenv/versions/2.7.2/bin/unicorn_rails)
ArgumentError: Already running on PID:☓☓☓☓☓ (or pid=/home/ec2-user/game-bug-app/src/tmp/unicorn.pid is stale)
  /home/ec2-user/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/unicorn-6.0.0/lib/unicorn/http_server.rb:206:in `pid='
  /home/ec2-user/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/unicorn-6.0.0/lib/unicorn/http_server.rb:138:in `start'
  /home/ec2-user/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/unicorn-6.0.0/bin/unicorn_rails:209:in `<top (required)>'
  /home/ec2-user/.rbenv/versions/2.7.2/bin/unicorn_rails:23:in `load'
  /home/ec2-user/.rbenv/versions/2.7.2/bin/unicorn_rails:23:in `<top (required)>'
bundler: failed to load command: unicorn_rails (/home/ec2-user/.rbenv/versions/2.7.2/bin/unicorn_rails)
ArgumentError: Already running on PID:☓☓☓☓☓ (or pid=/home/ec2-user/game-bug-app/src/tmp/unicorn.pid is stale)
  /home/ec2-user/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/unicorn-6.0.0/lib/unicorn/http_server.rb:206:in `pid='
  /home/ec2-user/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/unicorn-6.0.0/lib/unicorn/http_server.rb:138:in `start'
  /home/ec2-user/.rbenv/versions/2.7.2/lib/ruby/gems/2.7.0/gems/unicorn-6.0.0/bin/unicorn_rails:209:in `<top (required)>'
  /home/ec2-user/.rbenv/versions/2.7.2/bin/unicorn_rails:23:in `load'
  /home/ec2-user/.rbenv/versions/2.7.2/bin/unicorn_rails:23:in `<top (required)>'