Dog Has Swollen Nose... Don't Know What Caused It. Can You Help?

Unfortunately, there is not enough information in the question to provide a concise and clear answer. There are a few things it could be. If your dog's nose is swollen but there does not appear to be a wound, and it is the whole nose without any sinus leakage, your dog may have been in a plant or been stung by a bee. There are some allergic reactions that could cause a dog's nose to become swollen.
If the nose seems swollen and there is nasal discharge it could just be an allergic reaction. In this case there are medications for dog allergies such as antihistamines that could reduce the swelling and make your dog feel better. If you know your pet has this issue then you can dispense such medication without taking a trip to the vet.
Look at the nose to see if there are any wounds. If there are, your dog may have got into something it should not have. Keep in mind the wound may be on the inside depending on what occurred. Generally if the dog is outside during the day, I would consider whether some type of bee, plant or other animal may have caused the problem.
An indoor dog may still be able to get into situations that could harm them, but it is more difficult to say what it might have been. It is a better idea to visit a vet rather than to try and diagnose the problem online. This is because the professional will have more experience of what to look for. Furthermore, they will be able to ensure your dog is healthy. You do not want let a problem get extremely serious and go undiagnosed because you failed to provide medical treatment.

Hey my dog is much much better :) thanks for all of your great answers! He was really really swollen for about 3 days and after paying special attention to my baby boy, his swelling started going down! We are guessing he got stung by something, and there is a possibility he put his nose into an ant bed! But I really appreciate your help! We gave him soft food and warm milk; he also stayed in my bed, which has a mattress warmer on it! Thanks-Emmaleigh

A dog spends a lot of time with their nose near the floor or ground. A bee sting, spider bite or other insect that might be present can cause this. I've seen this with ours.

There is nothing much that you can do in the absence of the doctor but try giving him some hot milk or something hot. This may cause his nose to be cleared and thus become less swelled up. Other than that, stuff him in warm clothes. There does exist a likelihood that he has caught cold due to the cold wave that is present.