Drive the tube into the case, instead of filing the tube, you would need to polsih the tube if you file, just so it wouldn,t tear the rubber seal in the crown.
The screwdriver shown in the pic next to your watch is the tool you need. Insert the screwdriver in the tube, its handle wont enter the tube, tab on the screwdriver on its head to dirve the tube in.
Another approach is to drop bits of metal in crown hole where stem screws in, bits of solder, aluminm foil, screw the crown on stem.