After install the Nginx on AWS instance, and visit your public ip address, you might see the following:

This site can't be reached

xxx.xxx.xx take too long to respond.

Try the following steps to solve:

Go to EC2 Dashboard -> NETWORK & SECURITY -> Security Groups 

Select your current group, and right click, choose Edit inbound rules:

Add two items:

HTTP - TCP - 80 - Custom - 0.0.0.0/0

HTTP - TCP - 80 - Custom - ::/0

Then try to visit the public ip address again, hopefully it works like this: