realized today that one of of my spokes had come off the nipple! the nipple fell into the rim (?) i think and its rattling about it there. What do I do? I have like no bike fixing knowledge but im willing to try something if its cheap enough and if i'll get to learn to true my wheels for life! Otherwise how much will it cost to take to the LBS? also will they be able to get that nipple out so it doesnt rattle around??

Thanks!!!!!!!!!!!!!!!!!