Puppy has pimples?

I'm unsure if this is a serious issue or not.. My puppy had 1-2 pimples on her belly which I asked my vet and she said it's fine, it might be a light allergic reaction and it will go away on it's own.. However 2 weeks later there's more and it's just red lumps and some white heads with puss in them. I looked this morning to seeing a bunch of them around her groin area, I'll be taking her to the vet Friday, I just wanted to make sure I'm right in doing so and maybe get a second opinion.  

Hello!  We don't give second opinions here I'm afraid because your vet has much more information available to them than we do.  However, I absolutely agree that if something was expected to slowly fade but has actually got worse, your vet will want to know about that.  They might for example prescribe an antibacterial wash for the area or start to conduct tests.

I think it's what you implied, but always do go back to the first vet in these cases;  they know what they thought the first time / how it looked, so will have the best context and should be well placed to help you to decide what to do next.