Sorry, I guess filing isn't the right term here. You can use black emery to smooth, not file, the sharp edges. Black emery is a polishing compound and is available at any home improvement store. There's also another technique which involves heating up a very thin line on the glass and then cooling fast enough to where it becomes very brittle and hitting it gently. This is done by tying tying an alcohol drenched thread around the piece you want to take off and lighting it. Then you quickly put the piece under cold water and gently strike it with something like a piece of wood.
...yea, black emery would most def be the easier way to go.
Hope this helps.