ABOVE he/she is right!!!!
You can configure your rule statement in your WAF web ACL to Inspect the Header and set your Header field name to Host and finally specify a Match Type to a regex pattern.

FIRST you want to create a regex pattern so that if anyone hits your site with ip waf will block it.

open waf > (on left side) regex pattern sets > create regex > put name , description and region... NOW under Regular expressions copy this pattern given below :
^(?:[0-9]{1,3}\.){3}[0-9]{1,3}$

this pattern will match the all ip address.

NOW create a go to rule > add rules > add my own rules > put rule name > select regular rule > statement inspect > choose Single header > in header feild name write = host > match type = matches patten from regex patten set > under regex pattern set choose u r regex. then set Action to BLOCK > add rule....
NOW hit u r website with IP wether it is global accelarator IP , ELB IP or any IP depending on u r archeticture.