Dog Has Itchy Lump on His Side?

My poor dog has an lump on his side about the size of a quarter, it's hairless and he is now trying to scratch at it. When I first noticed it about a week ago, it was just scabby and raised, but now he has scratched the scab off and it looks so irritated. I've been putting Neosporin on it, but I'm not sure if I should take him to the vet or if it is something that I could treat at home. Other than the itching, he is still acting completely normal. He is also only 9 month old and he's a mutt. He's a mix of with Rottweiler and Pit Bull. The picture I uploaded is right when I noticed that he had scratched it raw and it started bleeding so it looks worse than it normally does.