"my dog is 14 weeks old and broke his leg has had a cast on for 4 weeks underneath the cast as he seems to be taking all the bandage off it is all red and a little scabby looking'does anyone know what it might be and will he be ok?"

I would go to the Vetrinarian in any case, especially if he's supposed to have his cast on still. If you're worried about Vet costs it sounds like he's probably just got some chaffing, rubbing and irritation from the cast and perhaps his fur is rubbing the skin in between the cast and skin. It should be a minimal cost for the VET to confirm this but the only way to be certain and for the dogs well being and health the dog should be seen by a professional. The other reason for going to the VET now instead of later is the potential for the issue to become worse and costing more to be treated as it becomes worse. Hope this helps.

If he is ripping the cotton out from under the cast, then he's getting rubbed raw by the cast itself.

The cast needs to be reset. Its going to get very irritated and itchy and he will never leave it alone. If any type of wounds or rashes appear, he could very easily get a staph infection.

Is there any type of immediate danger? No, but like I said, its probably really itchy and miserable. I'd call my vet and see about resetting the cast.