My dog grew a big lump on his back over night and then it turned green. When I applied pressure to it out broke open releasing green mucus. His hair came off and now He has a large open area with just his flesh showing. Does anyone know what this is?

Your dog needs emergency care! No use asking us , take him to a vets right now! That poor dog is suffering... When It comes to health please make sure you seek professional medical advice, because what you have just described sounds very serious and life-threatening for your dog! Good Luck and I hope your dog is okay!