I Had A Csection And Delivered Twins On The 4th.

I had a csection and delivered twins on the 4th. About the second or third day after, my left elbow on the inside became numb and tingly. They said it was prob fluid or from the spinal and to watch it. It became worse shooting pain down to my wrist. I went to the doctor and he was stumped. He sent me for an ultrasound to rule out a blood clot. No clots but they found thyroid nodules coincidentally. I just had a thyroid ultrasound today and I have a 1.37cm goiter. I read that a numb arm is a sign that thyroid cancer has spread. Would the ultrasound pick up cancer in my arm? Any ideas on what is wrong with my arm? What kind of doctor should I see?