Hey, welcome to the club 
. I believe that this is the topic we were discussing in a previous thread. It does seem like some sort of filament ooze that makes this dark tar substance. I can only get my hot-ends off by heating it to 200°C.
As for cleaning up the gunk, I just went in with a fine razor and scraped it off, might also help to heat then scrape. Be careful as to not create any large bumps that’ll offset your nozzle.