What part on the Ender 3 v2 is this and can I just get it as a replacement?

[Dko]

Hi.

New to 3D printing in general so be kind. :)

I have my first printer, which as you can tell from the title is a Ender 3 v2. I have already done a lot of learning (aka breaking) while using it and had to already replace the hotend once. (If you really want to know, I didn't heat the end up enough and snapped it off like a twig, with the threading still inside the heat block. :/ )

My latest problem is in an attempt to find out why my filament wasn't flowing right, I tried taking out the tube... and ripped out the toothy metal wring that is inside the nut near the top of the heat block (picks attached). What I want to know, is the name of that bolt and if getting a replacement is easy or do I have to buy ANOTHER hot end?

Thanks in advance for any help.