Accidentally shaved down tooth, what can I do?

I definitely recommend building up the edge of that canine and am against shaving down the one on the other side. Canine's have the important function of protecting the other teeth when you slide from side to side. This requires them to have their pointy appearance. If it's not too substantial of wear, you can add composite bonding to the edge to return it back to it's original length and restore function. 

First of all, you need to stop the habit of biting on your nails or this will continue to be a problem.  Simple bonding of composite filling to the canine may be able to give you back the pointy canine look you desire.  This would be the least expensive alternative.  However, if you continue the habit you will wear down or break off the new bonding as well.