Don't be scared! Everyone gets nervous when it comes to matters of the heart. I am 16 and I still get scared to talk to the boy I like. You just need to think of what you can talk to him about, what kind of things you think he would be interested in that you both have in common so that you wont run out of things to say if you do take the risk in saying hello and talking to him. You need to get over your fear and just take the plunge! If it does work out then you will be glad you did talk to him but if it doesn't at least you know you tried. If you just continue to notice from a far then you will be stuck wondering what would have happened if you did talk to him. Good luck && I'm sure you will be fine! :)
Just remember to breathe and have the self confidence that you can do anything and that any boy is lucky to have you.