hi, Im having a problem with nick , i did a few missions with him and now dropped him off at sanctuary hills , but he keeps walking off. I'm afraid if I don't follow him , he will disappear and I wont be able to find him again. Does anyone know where he's headed. Does he go back to diamond city?

With some companions, there may be glitches where they will return to their original location even after you assign them to a new settlement. Nick is probably back at the Detective Agency, nothing you can do about it since that file is forever glitched.

If you drop him off at Sanctuary Hills he should stay there, unless you have some quest active in which he ends up waiting for you at some other place perhaps.

ok ,thank you. I can stop following him now, lol

In between two particular quests he goes and waits for you at the memory den.