Ouch, I remember that after they had to go in thru the out door and grab the stone. I did not have the fluid buildup, but for the first couple days after surgery it felt like I was peeing burning sand. Yes, you should probably call the uro.
Yup, I've had that little string before too! I did not have the fluid buildup you are talking about though. If it's bad, you probably should call your Urologist and ask him/her if they want to check it out.