It could be CL, but the fact that it developed suddenly overnight makes me suspect that it isn't.  Abscesses can be caused by any number of things and CL is only one of them.  If it is CL, DON'T PANIC!!!  There is a lot of hysterical alarmist nonsense out there about CL and much of it is put out by people who should know better. No matter what anybody, and I do mean ANYBODY, tells you, CL can be controlled and eradicated and you can prevent other goats in the herd from getting it. The most important thing to do is to never allow an abscess to burst out in the barns or corrals.  CL is spread mostly by exposure to pus from a draining abscess.
I may not know everything there is to know about goats but I do know about CL.  I first started raising goats in the late 60's and at time many herds, including mine,  were infected with CL.  I got rid of it and so did the other goat keepers I know.  We didn't burn down the barns and corrals and we didn't isolate or cull infected animals to do so either. I would much rather deal with CL than either Johnes or CAE.  If you need detailed instructions on how to safely lance and clean abscesses and how to control CL contact me.  Just send me a PM. I know this protocol works because this is how we all got rid of CL once and for all, and it never, ever came back.