Firm knob comes & goes beneath liver

As you point out, this is difficult to comment on without knowing all of your other signs and symptoms. Additionally, Chinese Medicine doesn't diagnose per se, but uses all of the signs and symptoms to come to a pattern which it then uses to treat from. You should consult your physician about this issue as there are a number of things, both minor to serious, that this could be.

The first thing that comes to mind would be either some stagnation in the large intestine, perhaps some pouching in the area (i.e. diverticulitis). Also, the gall bladder is in that general vicinity, so a nodule there is possible. On the more benign side you could have strained abdominal muscles that react and tighten for some reason.

I would see your physician first and if all checks out well see an acupuncturist in your area for proper diagnosis and treatment. Before you see your practitioner you should take special note of when you feel the nodule arises and when it recedes. Is it after large meals, after any meal, after alcohol, - in short, what makes it appear. Also, how long does it typically stay active, what, if anything, seems related to it going away - a bowel movement, fasting, exercise...