You have photographed a gall, which is like a cancerous growth on the plant with the extra growth triggered by invasion of a foreign entity such as a fungus, bacteria or larvae stages of wasps or beetles. If this wattle is indeed Acacia penninervis this wattle is regionally uncommon and not previously recorded in the Queanbeyan area.
I think it probably is, but would like to see a photo showing more clearly the vein between the gland and the base of the lesf. This is diagnostic. For an imoortant record like this it pays to be certain.
I have actually confirmed it, after checking my photo of it from Black Mountain. To be absolutely sure, a close up of a leaf showing the gland on the edge would be great. Don't worry about the gall. Woody galls basically all look the same.
I suddenly realised it was more likely to be Acacia pycnantha, which has much broader leaves than Acacia penninervis. It is quite common on Mt Jerrabombera, at least.