Not sure about afterwards, but I was GBS positive with both my pregnancies and was given antibiotics before I actually delivered. Did not have any issues with it.
Your baby will be fine, it's only really a concern during the birthing process. It's a normal bacteria that is in your body at all times, and sometimes it gets a "colonized" or there is more than the normal amount. It's harmless, except to an infant, but only during childbirth is there a risk of infection for them. You can also be positive at one point and negative later- the antibiotics don't really "cure" it but they do go back into balance on their own. I had it with my first, and then not again until 16 years later with my most recent baby.
Hm. Interesting question. So, did you take antibiotics for the GBS? How long ago? Was it cleared before you gave birth? You may no longer have it if so. I am guessing your child will be just fine.