What is causing growth?

[brushcreek]

I have a 6 week old pup that has a large growth on her head. I thought it was infected from maybe a house cat or other wound however since I tried relieving the growth by opening it up and also giving pup penicilin the growth has only gotten larger. A friend of mine said it could be from the cold weather? The bitch wont allow any pups around her any more (ever since 4 weeks old) so they were sleeping by themselves outside of a dog house until I got them a dog house for them about 4 days ago. The growth started about 6 days ago.