Nginx: Allow All But Block Certain POST Request URLS For Selected Spammer IP Address/CIDR

I am a small business and ecom site owner. I also run a WordPress based blog to connect with my customers. However, I get too much spam from certain IPs and net-blocks. How do I block access to certain url(s) such as example.com/blog/wp-comments-post.php for selected IP address and CIDRs? How do I allow everyone including IP address 1.2.3.4 to access my blog but block IP address 1.2.3.4 accessing only example.com/blog/wp-comments-post.php? How do I block POST requests for selected IPs/CIDR on nginx?