iptables rule to block local net port

I'm on local 192.168.1.0/24 network with an openwrt router at 192.168.1.1 and I want to block any tcp connection to an IoT device that has an open port, let's say 192.168.1.12:5001. I don't have access to the device's linux so I can't enforce the rule there, Is that even possible from the router without any complex segmentation? maybe I need special router/switch? I have tried these on the router, but none of them work:

root@OpenWrt:~# iptables  -I INPUT  -p tcp --destination-port 5001 -j DROP
root@OpenWrt:~# iptables  -I OUTPUT  -p tcp --destination-port 5001 -j DROP
root@OpenWrt:~# iptables  -I FORWARD  -p tcp --destination-port 5001 -j DROP

(I'm fine dropping any packets to port 5001 just for testing)