When I first started knitting I would also get sore arms, and a sore neck and back. My teacher stopped me one day and told me to put down the needles and get up and walk around a bit and stretch my hands, arms, and shoulders. I was so nervous that I was going to mess up my knitting that I was holding the needles really tightly and hunching myself up. I just had to figure out a comfortable way to hold the yarn and not clench my hands around the needles, and then I started relaxing a little. I don't know if this helps or not, but that's what worked for me. Good luck!