Ahhhh the Mandolin, once you get one, you'll never put it down
Most guitarists I know really get a kick out of playing them. They're tuned like a violin/fiddle though, so you can't transpose your guitar skills directly in terms of chords...
If you like that sound on Nickel Creek, you should try listening to one of Chris Thile's (the mandolin player) early albums, back when he wasn't so technically mindblowing, it can be fun to chop along to. The album I'm thinking of is Stealing Second, and playing with Chris Thile are most of bluegrass's star players, so it's a nice introduction
As for stuff that sound like Nickel Creek, I'd definitely recommend Alison Krauss & Union Station. Alison Krauss produced Nickel Creek's first two albums, so they do have similarities in sound. I'd recommend her album So Long So Wrong, it's kind of middle-of-the-way in terms of bluegrass, easy listening but bluegrassy enough to get you hooked and wanting to explore it more!
Also in a similar vein is the band Mountain Heart, try the album Wide Open.
Definitely Crooked Still.
The Lovell Sisters, very instrumentally pleasing but more mainstream so easy to start with.
I've spent my life trying to convert my friends to bluegrass music
, and I've found the bands listed above definitely were a good place to start
I look forward to hearing how you get along!
Listening to:
Robert Earl Keen - Blow You Away