If I join The Institute what happens to Nick?
I met the Institute and I kind of like it, the only thing that i worry about is that if I join I could not interact more with Nick Valentine. Does anything change with Nick if I join the institute?
No, if you join the Institute nothing happens to Nick. He is still available to use as a companion and it doesn't appear to effect his standing with you. It will however open up a few passing comments where he'll query why you're working for them.