I just got my first client and I'm insanely nervous

Okay, so here's the story.

I'm a student in a 4 year program, currently in my 2nd year, and came across a flyer in my schools art building looking for someone to create a "unique identifier" for their startup restaraunt.

I'm always trying to find ways to improve myself, so even though I'm a little unconfident in my abilities, I went ahead and told them that I would try and do it. I'm basically winging this entire thing, as I've never had a client before and figured that I would never learn more about freelance graphic design if I didn't just do it. But the thing is, I'm super nervous and I'm starting to second guess and doubt my abilities because I'm still a student.

They want to meet with me tomorrow and even though I'm really excited for a way to improve my design abilities, I'm actually really scared they're not going to like my work because I'm still a student.

What's a professional way of saying "I would love to try and help, but don't turn away other people who are looking to help you because I'm unconfident in my abilities and afraid that you won't like my work" I think if I invest a lot of time into this then I'll be able to come out with something decent.

It just feels weird that they're going to trust me to create their logo. Kind of a lot of pressure. OR, if I'm second guessing myself this much should I just back out all together?

Sorry for the rant, I'm just really damn nervous

EDIT: just a thought, if I'm just doing this to try and get better, should I do it for free?