My son has scratched my wok. Now it's rusting. Can it be restored or should I throw it away? It says Made in Japan. It's heavy and matte black. Can't post the pic due to size limitations.
Yes, you can restore it.

Clean the whole wok. Wash with soap and dry it. Apply a small coat of oil and put it on high. Let it burn (ventilate the kitchen).

Repeat the process of applying a small coat of oil and putting it on high another two or three times.

Done.

Edit: As noted by @GdD, this method cannot be applied to non-stick woks.