Worried I just ruined everything :(

I like this guy in my class called Brian. Brian is also my friend. I moved schools in September and I met Brian when he sat in front of me in English class. We often walk to class together and he comes over to our friends at lunch. I read a few sites on things like "How to tell if a boy likes you" and I checked for some of these signs- and found them. I'm quite shy when it comes to talking about boys, even with by BFF. I wrote him a note asking him out and put my nickname (of his invention) on it. But when his best friend came over and said "Is anyone whos initials are AL here? I knew I was in deep trouble. My nickname is Lala and so I signed the note LALA but they read it as AL AL. I put anouther note in his locker telling him that it was me but now I'm terrified, what if he says no? What if it ruins our friendship? I never wanted this to happen! So what should I do now? The problem is, I've got exactly two days if I want to get the note back, and I do but that seems impossible. So what should I do? Pls help as everyday I am sick with worry and I don't know how long I can carry on pretending that it wasn't me who sent Brian the note.