great advice from tanglewood. Please let us know what you found out.
I would call his doctor immediately - that sounds scary to me. I'm sorry your dad is suffering with this and I can relate to what you are going through. My dad died of cancer and it was the worst thing I ever had to endure. Watching your dad suffer is so hard. Good luck, I hope your dad gets better.
Don't know if this info will be helpful in your case, but I have problems with my right arm. When I don't take my pain meds my arm hurts, swells up, turns blue, and is cold to the touch. I think it is because muscles in my back tense up and cut off circulation, but I'm not a doctor and my doctor's don't seem to want to talk about it. If the pain meds are not helping your dad I think you should call his doctor - good luck.