Mr

[Domino05]

My dog has a bussy sore on the back of his neck which is not getting any better, is there anything I can do? I think this was from a insect bite? was first noticed a week ago as a small lump, it has now spread down the back of his neck.

[Margot49]

Glad you had it checked and hope all goes  well.
Thanks for the update which most posters often don't give us.

[Domino05]

thanks for the comments took him to the vet it is wet eczema being treated and looking better already

[1grrr]

I'd say abscess or cyst, or a cyst that has abscessed, and I'd say too, a vet and no doubt antibiotics are in order. This isn't something I'd treat at home, for all the reasons the previous commentor stated.
Good luck, and I hope a vet appointment is imminent.  

[Margot49]

Sounds like this may be an abscess which should be seen by a Vet.  The dog would probably need antibiotics and need it lanced or a drain put in.  
If it has spread, I don't think I would try to treat this at home.  Hope you get to the Vet.