/diy/ - Do It Yourself

>extruder clogs
>take apart the hotend
>the heat break is full of sticky grey stuff that doesn't want to come out

What is this?
I assume it's melted, polluted filament that's built up in there and not some adhesive for the bowden tube or something, right? Should I be worried about getting it all out to make sure my bowden tube seals the inside properly?