It could either be mites or an ear infection. Codie is prone to getting ear infections -- so I always keep a supply of ear drops (from my vet) at home and on hand -- those drops ger rid of the infection right away.
I clean Codie and Tia's ear every day with a q-tip (part of their daily grooming). If you clean your pups ears with a q-tip and a thick, dark (brownish black) discharge comes on the q-tip, your dog probably has an ear infection (could be from getting water in his ear during a bath).
NOTE: When you put the q-tip in your dogs ear, DO NOT push it all the way in. Be very careful not to damage the ear and/or hurt your dog. You should GENTLY skim the surface and only go slightly into the ear canal ... but VERY slightly. Only a vet or trained professional should go deeper into the ear. If it's done wrong, serious injury can occur. So be careful.
BUT, I would still highly recommend taking your dog to a vet FIRST and FOREMOST before trying any of this. The only reason I clean Codie's ears myself is because he gets frequent ear infections and the vet taught me how to properly care for it -- as well as gave me a big supply of ear medicine.
Good luck and I hope baby feels better soon. I bet his little ears must be so itchy.
Codie and Tia send him kisses!