Hi guys!
I want to block all input/output to a specific IP from everyone except my LAN
I have an idea but I’m unsure if it will work
for allowing my LAN and drop everyone else
/ip firewall filter add chain=forward src-address=x.x.x.x/24 dst-address=!192.168.x.MyLAN/24 action=drop
It would be best if you provided a bit more detail.
For example if one was to read your title, one could interpret the request to be that your LAN can ONLY access one IP address, and no others. 
How many LAns are there?
Which Lans are users located on?
Lets say you are the only person on LAN1
Are the rest of users are on LAN2?
The IP that needs to be blocked, is this on LAN1 or LAN2 or a third LAN3?
I hope you see that more detail is needed to nail this down.
there are 3 Lan
That was a near perfect answer 
Post a drawing with all VLAN, IP, interfaces, name of everything +++