What should I do if my Bearded Dragon has a large lump in his neck?

I am sorry to hear about all the trouble you have with him. Unfortunately there is no magical cure and nothing that you can buy over the counter to help him. Usually an abscess are caused by bites from insects (feeders) and the small injury grows over time. It can also be a cyst or a tumour and only a vet can treat it and prescribe antibiotics. You can read up on diseases here, can you possible post a photo? a href="http://www.reptileparrots.com/t112-is-my-bearded-dragon-sick" rel="nofollow"http://www.reptileparrots.com/t112-is-my…/a