Cat claws and cat bites given during fights are great at causing absecces. This is probably what she has, sounds like it has burst open. You need to take her into your Veterinarian to make sure this...
If the lump is in the cat's fur, it is just a knot. If it's on the skin, it might just be a wart or a skin tag. But if it's under the skin, it could mean something serious. You really need to get...
There can be many different kinds of lumps, and the diagnosis will depend on things like how firm the lump is, how long it took to grow, whether it causes pain, whether the cat has a fever, whether...