Identifying a Lump on Dog's Ear?

So this raised lump showed up on my 15 week old English Staffy, at first it wasn't very noticeable as it was covered with hair. The vet said he may have been bitten by something. A week later it looks like this? We have had to put a cone on his head as he kept scratching it and making it bleed. This is it a few days after he has had the cone on? The lump is firm to the touch. It isn't sore in anyway and the lump almost feels like a oval shape. Any ideas on what it is? And should we be worried?

Thanks.