Skin Discolouration?

My supposed "good arm" is the one that has the pic line running in it, which is how they are putting the antibiotics into me daily. I have been complaining about it a little for a couple weeks now, that there are some tender areas in the upper arm. The nurse has been watching for any signs of a blood clot, and there aren't any, so we have just put it down to me being a little grumpy with the whole thing. But today we noticed that I have some dusky discolouration on that arm. At first, I got a washcloth and scrubbed my arm, thinking that it was dirty. But its not dirt. So the nurse called the hospital and they have bumped up my appointment with the ortho surgeon to tomorrow. He will take a look at it, and maybe nix the whole antibiotics thing (I only have a week and a bit to go). And hopefully, he will still take the xrays of the surgical arm, so that we can see what is happening in there!