There is no evidence of any sort anywhere for the existence of a planet called Niburu. Therefore there is no likelihood of a collision of it with anything.
What we DO believe however is that some time in the future, as solar orbits decay, a gravitational interaction between Mars and Venus will result in one or the other being "thrown out" of the solar system. Since Earth's orbit is between the two, it is possible that this will be bad news for us also.
You should worry little however, this event is probably a billion years off yet.
