Nolva will bind to the receptors preventing any further gyno development and you should be taking it for this reason. 20mg a day is enough.
If you are lucky it may reduce some tissue growth. Very unlikely to fully reverse gyno development and it might not reduce it at all.
What the nolva will not do is lower your estrogen which is what has caused the problem.
You need to take an AI - arimidex, letro or aromasin are all fine. If you do not get estrogen back to normal then the issue returns when you stop taking the nolva.