My iPhone 5s keeps saying No Sim Installed?

It's getting really annoying. I'm sick from school today and I'm trying to call a relative cause it's his birthday and I can't. It didn't say this yesterday or before that (I just got the phone like 2 weeks ago and it was used by my aunt in Australia, I live in WASHINGTON btw). It HAS a sim card. IT DOES.
So how do I make it stop like right now? I'm 15 and sick right now. So I can't drive to a store and pay like $50. Help. 5 points to the most reasonable answer!

Try wiping the sim with a dry cloth, it may have been damaged during the trip and finally broke today (just bad luck). If that doesn't work, you need to get a new sim ($10) from your carrier.