Small lump on his penis

Hi everyone,

I’m probably worrying about nothing, but for a little while now my dog has been nibbling at his tail and his bum, and he occasionally nips at his balls too :/

I’ve been to see the vet who said it might just be a small itchy sore, so he had a steroid jab (I think), but nothing has changed.

I went back to the vet and we decided to give him some medication to calm him down, as she thinks it’s a behavioural issue.

But he’s still nibbling away.

Coming home from work today, I noticed two little lumps in the middle of his penis area.

I’ve no idea if this is normal or not?

If anyone could give me some advice on why he’s nibbling himself and whether this lump on his privates is normal?