Asteroid 2015 HR182 is a 200~400 meter asteroid discovered back in April of this year. Unfortunately it was only observed on April 18th and the 21st and then it was lost due to unfavorable observing conditions. In fact it was at a very dim magnitude of 23 when it was discovered, so only one observatory was able to see it at all on those two nights. This means that the orbit is highly uncertain and we have now lost the asteroid; the orbit is too uncertain for us to even know where to point our telescopes in order to locate it. If it is on an earth-impact trajectory it would currently be closer to the sun than earth and essentially unobservable since it would be on the day side of earth.
An asteroid of this size would not wipe out all life on earth or end humanity, but it would form a large complex crater several kilometers wide if it were to hit land. Basically it could wipe out a city off the map in an instant and tremors from the impact would be felt hundreds of miles away. The good news is that the odds of impact are only about 0.0000000000221%; earth is a tiny speck in a huge region of space where the asteroid could be located. So chances are nothing will happen.