Coppers Rash

Could be anything.    Hives, reaction to a bite, an alergy.  best to give benadryl - However not sure how young you dog is so follow this guide for dosage -

Benadryl
Use: Allergies, itching, reaction to insect stings, etc. *hives, minor swelling
Dosage: 1 to 2 mg per pound body weight every 8 hours

If it does not clear up, or gets worse, then contact your vet.

Benadryl is a good start, keep an eye on him and if doesn't seem to be going away, take him....Hope he starts feeling better

Yeah thats what i'll do. A little benadryl. he is fine and not itching it or anything but i get worried over any little thing on my little boy .