Possible Puppy Surgery

So my puppy has had “allergies” from what the vet has said and she had some hot spots that after medication and changing out some things like detergent and shampoo, have completely disappeared. There’s one bump that has gotten bigger, I’m assuming because she is able to reach it easily as it’s on her lower back and has gotten infected. We brought her to the vet today to check it out and they gave her antibiotics and mentioned potentially doing surgery to remove it and have it biopsied if it doesn’t start to shrink. Has anyone had experience with something like this? I trust our vet and I’m not asking for health advice, more just how you handled the situation and if pet insurance (I have spot) was helpful. I’m praying the meds work and we don’t need surgery but I’m obviously stressed about it. She’s 16 weeks.