Ganglion cyst first knuckle middle finger What causes it? What can I do to get rid of it? Would having long time acrylic nails have anything to do w/it?

No. there are few reasons, but never seen nails to be the cause, ( unless you used acrylic nail on middle finger only). Most cyst will resolve after few weeks. Wait and see, don't mess with it. It keeps getting bigger and does not go away surgeons can help.