AWS Instance: ping not reaching

I created a micro-instance for some testing, and set it up. I installed Docker, and ran simple Nginx image.

Now from the host, when I do

> curl localhost

It works. But when I try to access the same with my given public IP, it does not work. (returns with Error code: ERR_CONNECTION_TIMED_OUT on Chrome).

Could this be because I changed the hostname from ip-172-31-X-X to something else?

I also ran nmap -sT -O localhost to verify that port 80 is open:

Nmap scan report for localhost (127.0.0.1)
Host is up (0.00030s latency).
Not shown: 998 closed ports
PORT   STATE SERVICE
22/tcp open  ssh
80/tcp open  http
...

But ping is not working, neither am I able to access the index page via public IP. What's going on?

Reference:

http://ift.tt/1AAmkP8