It may be itching due to allergies or infection or a fungal infection.
Sometimes they hit the chin when the real problem is th ears itch so checking them may be worthwhile.
You might want the vet to check for ringworm and you can read about that infection here
Benzocaine is on the list of meds you should never give a cat. Lidocaine also isn't very safe and should only be used under vet direction.
If you happen to feed out of a plastic dish you may want to try using stainless or ceramic as some animals react to the plastic.
You can use a topical antibiotic ointment (no pain relief ones) such as Neosporin to speed healing.
If you really want to keep him frmo scratching it the dreaded lampshade collar may work and your vet can fit your cat with one or you might try this alternative to see if it works
Hope this helps you!
No there is not a topical anti itching product safe to use with cats without direct vet supervision.
When the lampshade collar is on the cat cannot get it off and they do get used to it over time. The alternative collar might also work for you and its far less bulky for the cat.
Cats keep boots on about as well as they keep on bandages but you could see if claw covers like these soft paws would help