Should I Be Really Worried???

I noticed this small lump on my dog a few days ago and I've been monitoring it. Tonight I checked it and it was probably 3 times larger than before. I'm calling her vet in the morning but I'm just wondering how worried I should be bc I'm freaking out at the moment. She is my world and the thought of losing her is absolutely devastating. I'll do anything that needs to be done to help her but I am just wondering how serious this looks. She acts fine overall. Running and barking with the neighbor's dogs when she goes outside and playing with her brother and sister inside. She has acted a little more lethargic today but nothing super worrying. Like I said, I'm calling her vet in the morning but I just want to see if anyone knows what it might be. Thank you in advance! (If anyone notices the part of her ear that is missing and think she is a fight dog, she absolutely isn't... she was attacked by one of my neighbor's dogs. They broke through their wooden fence and my chain length fence, managed to grab her head and attack her. Along with many other injuries they tore off part of her ear. After getting the police and animal control involved those dogs are no longer there. Zoey (my dog) doesn't even go to that part of the yard anymore. Luckily, I have a large yard. She plays with the other neighbor's dogs now).