He's saying you should use sandpaper to get rid of the gunk from the tip.
Most cheap tips have a copper core, which will sand/file just fine. Once the gunk is gone, heat it up, flux it, tin it, and wipe it with a moist sponge/cloth.
If you have some expensive alloy-tip, the sanding may wreck it, but it sounds like it's already wrecked.
If you have acid you can use some to clean the tip.
Your carpet is most likely made of nylon which is plastic.
Acid will clean off the plastic but the tip which is made of some kind of metal won't be affected.
Be really careful with the acid if you choose to clean it that way.
Once its clean, wipe of the tip with some sponge or something. If you just leave it to dry, it will get some weird color but other than the coloring it will be fine.