I have IPWebcam running on an old cell phone so I can monitor the printer from upstairs or outside of the house. I had started a print with a fairly full build platform and checked it before going to bed. I saw one corner didn't look quite right, but I was tired and thought I'd sort that out in the morning. Big mistake! Here's what I woke up to:
While things were still hot, I grabbed a heavy shop paper towel and folded it over a couple of times. I could drag that across the heat block and extruder tip. It picked up all of the melted PLA after several tries. Be careful to not wipe the hot end with your fingers behind the paper towel. Hold a longer piece between your 2 hands and rub it over the PLA on the hot end so it drags the plastic off.
I cleaned the heating element and as much of the thermistor in much the same way. I was able to heat it up again and re-insert it to re-heat the hot end when I wanted to get more PLA off. I was also able to get the paper towel in above the heat block and clean off the threaded tube.
I found the block was loose and so, I used some pliers to carefully twist it tight again. That threaded tube is not super strong, so don't torque it too much! I cleaned out the hole where the heating element went and reinserted the element. In the past, I had a single layer of aluminum foil wrapped on the element so it was pretty snug in the heat block. I did that again and got it all back together. It's looking pretty good now!