This is Dr. Christian. Welcome to JustAnswer.
Thank you for the information. It sounds like Toby is having an allergic reaction. He is showing the common symptoms for that. You may not ever figure out what he is reacting too but a common cause is an insect sting (such as a bee). You can give 50mg of benadryl every 8 hours for the next 24 hours. Make sure to call your vet in the morning to let them know he had a reaction so it can be marked in his record. The benadryl may make him sleepy. If the swelling does not improve in an hour or two then have him seen by a vet tonight. He would probably need an injection of steroids to get things under control at that point. If he starts to have a hard time breathing then have him seen by a vet immediately. If you have more questions please reply back.