Move the toolhead high off the build plate to give yourself room to work. Set the hot end temperature to somewhere in the filament's melt range and let it soften a bit. Use needle nose pliers to gently pick away at blobs of filament, making sure not to damage any thermistor or heater core wires in the process. If you want to salvage that hot end, follow-up with a brass wire brush while it's still hot, otherwise just remove enough goo to access the screws you mentioned.