Unless one of you move out, you'll have this situation for quite some time. Sorry to say, but you share the same problem as a million other people around the world.
Whether it be at school, work, your residence...it's part of life.
I don't know you whole situation, but keep in mind...even the police can't help you (unless the neighbour causes harm to yourself, your family, or your belongings).
Hopefully things get better. Good luck.