The easiest way is probably through the official Mapper.
So first get that and also some program that can compress/decompress in gzip format (I use the old command line program gzip.exe).
Then go to your latest save game slot and find the map file you are currently on.
Lets say you are on the first map in New Reno, then that would be NEWR1.SAV.
Rename it to NEWR1.gz and decompress. You will end up with a file called only NEWR1, so change that to NEWR1.MAP.
Move that file into your DATA/MAPS folder (If you already have that map in there you will have to move it out temporarily).
If you are not playing with the RP or the unofficial patch, chances are you don't have a MAPS folder. Just create one if that's the case.
Start the mapper and load the NEWR1 map.
In the drop down menu in the lower left corner choose 'Critters' then click Sulik on the map (make sure he gets a red hexagon under him).
Push the edit button and then "Flags". Set "Flat" and "NoBlock" to "NO" and then save the map.
Remove the .MAP ending and compress the map file. The rename it to NEWR1.SAV and place it back in your save game slot.
Don't forget to put the original map file back in your map folder if you moved it out from there earlier.
Then start your game and hopefully Sulik is back to normal.
You can get the BIS Mapper from here:
https://www.mediafire.com/folder/2aheaguwymint/Welcome_to_Fallout_Database#7pf9h8eowufc1
It's under "Fallout Modding Tools" and "Mapping Tools"
If you are playing with the RP you will also need to patch the Mapper with the City limit patch (you can find it in the same place as the Mapper).