I would be asking myself why the nock isn't tight anymore. Is it the nock or the arrow? Put a different nock in it and see if it's tight or not. If it's not you might have bad arrow and I would not risk shooting it.

If you have a vane missing or really messed up yes it can effect flight, but probably not too bad with field points. It will be noisy though.

If this arrow has these problems because of contact with another arrow I say trash it just be on the safe side.

Paul