How to fix this path issue?

Side note: When posting code here, enclose the code between lines of three backtick - ` characters. This means you’ll have a line of ```, then the code, then another line of ```. This forces the forum software to keep your code properly formatted. (I’ve taken the liberty of modifying your original post for this.)

Unless I’m missing something here, you should be able to change this:

To this:

        alias /home/ubuntu/petangel/staticfiles/;

(This should also be done for your /images/ alias.)

See the docs and examples at Module ngx_http_core_module

Side note 2: I never recommend granting permissions into a home directory to nginx. I always recommend that in a deployment environment that both static and media directories reside completely outside the directories in which the code itself is stored.
See my comment at Django and Nginx permission issue on Ubuntu - #2 by KenWhitesell for more information about this.