That's not a cassette, that's a freewheel. Since it's just a 2-prong one you can pull the axle and try to use pretty much whatever(like a file) as a tool bit. But if you haven't got a freewheel puller you probably haven't got cone wrenches either, which puts you back at square one. freewheels are notorious for sometimes being fiendisly tight, so improvised tools are just asking for failure. Do it right, get the tool.

OR get the lbs to do it for you, it's a quickie.