I might be wrong, but in a previous comment [0] a few days ago I noted that the asteroid composition is mostly ice, which means it should be much less dangerous than a "rock".
> Lakdawalla said that while the asteroid’s close brush with Earth may have sparked some concern, “it is zero percent danger to us. It’s the kind of thing where you learn about something that you didn’t know about, like things flying close by us, and your inclination is to be scared,” she said. “But just like sharks in the ocean, they’re really not going to hurt you and they’re really fascinating to look at.”
[0]: https://news.ycombinator.com/item?id=20508618