It sounds like your dog may have been bitten by something and/or is having an allergic reaction. I would take the dog to the vet and see about getting medication to help. An allergic reaction can be a very bad thing. Good luck!
Over Night My Dog Got Open Sores Around His Mouth Foot And Leg, Does Anyone Know What That Might Be?
Allergic reactions typically cause hive like lumps beneath the skin or facial swelling. Open sores are not common unless the dog has created them via self-trauma. Open sores may be infected sores or are at a high risk of becoming infected. Your dog needs to be examined by a veterinarian to determine the cause. One concern I have is multiple spider bites--spider bites can start to cause skin necrosis (skin death) and open sores. You need to keep your dog from licking and chewing these sores--this will bring bacteria to these wounds and will prevent healing.