How can I setup “RoadWarrior” wireGuard tunnel without a public IP address? I am receiving a private IP address [192.168.88.2] from my ISP.
I’m replying to you over WireGuard configured for this very situation. 
Thank you for this. Could you elaborate more on how you did the port forwarding? “Since my RouterOS box is behind another router, I forwarded this UDP port to it.”
I did this.
/ip firewall nat add chain=dstnat dst-address=192.168.1.1 protocol=tcp dst-port=13231 action=dst-nat to-addresses=10.10.10.1 to-ports=13231
where 192.168.1.1 is my local router lan ip address and 10.10.10.1 is the actual public ip address from the isp router
You don’t do the port-forwarding on the RouterOS box; you do it on the ISP router. Even if you had named it, the how-to of setting up a port-forward on it from the public WG port you picked to the RouterOS box behind it answering the WG connection would be off-topic here. That’s why my guide links you to this generic port-forwarding guide.
Thank you. Worked like a charm!