Why does my dachshund have a bump on his nose?

I have a five month old dachshund and whenever we leave, we put him behind a fence in my house because he always chews everything up. Well when we came back, he had a bump on his nose. He's never had this before so we thought it was from him trying to get out of the fence. We felt the bump and it was really squishy so we don't think it's a scratch or anything from him trying to get out. We've pressed on it and he doesn't whimper or bark so I'm guessing it doesn't hurt. Does anyone know what could have caused this? Is it anything to worry about?