Can you give a general approximation of the centimeter size of an linguinal lymph node in the groin area? what is a normal size and an abnormal size?

Size doesn't matter: It's common to find nodes up to 25 mm or even more on physical exam or autopsy. If your lymph nodes are not woody or tire-rubber hard, preposterously enlarged, or very stuck to the nearby structures, stop worrying about them. When I was a kid going barefoot in the summers, I blew up a few big ones on either side. Life's hard enough without obsessing that your normal lymph nodes are lymphoma.