As you know this formum is not for emergencies and you should take your dog to the vet ASAP.
Pain and swelling as you describe is usually due to a sting or insect bite or traumatic penetrating injury.
What you need to do:
Get this Puppy to a Vet ASAP....She clearly has something that needs to be addressed.....Don't make her wait & hope she gets better.......She's trying to tell you that she needs help.......Please, come back and let us know what you find out.....
I didn't have money to take her to the vet, but I did consult one online. I gave her a little bit of children's tylenol and children's benedryl. She's back to her normal playful self today, which is a relief to me, her sister, and my kids. The swelling has started to go down, she's eating (a lot) and drinking fine now, her nose is cold and moist again and she's doing great. If there is a relapse, I will definitely try to borrow the money from somebody, if I can. It's hard being disabled and living on a fixed income. =(
Benadryl was going to be my first suggestion. It sounded like she was having an allergic reaction to something which could have been even a bug bite of some kind. Or to a shot she received, if any recently. Anyway, I'm glad to hear the Bendadryl helped some, thanks for the update.