Please help!

I felt what felt like a crusty scab on my dog's head yesterday as I was petting him by his ear. Pushing the hair aside, I discovered what appeared to be a large open wound covered in numerous tiny scabs. Is there anyone who knows what this might be?

Hello - I'm afraid that given the  description, there are many things that it could be.  One is some kind of superficial pyoderma, eg a skin has been scratched and oozes, then sometimes dries into scabs. It looks like infection and once it would have been treated with antibiotics, but these days an antibactetial shampoo is often given instead.  Another set of possibilities include fleas, otitis, mites and other causes of itchy dermatitis.  The ear is a common site for dogs prone to allergy to scratch and sometimes to injure themselves in the process.  But I can't rule out a cut or wound eg from a scrape or bite.  Even tumours sound possible.  It does sound as though your vet should see this; treatments could range right across the spectrum, depending what they find.

I should also mention Ringworm, which may be passed on to humans.  Ringworm does sometimes itch.  For this reason, it would be a good idea to wear gloves when touching your dog and wash your hands afterwards, until you have a diagnosis.