I suspect that your cast on is too tight. You should be able to slide it on your needle and it shouldn't be a struggle to knit. Here's something to try--hold your two needles parallel to each other, points facing the same way. Cast onto the two together and then slide one needle out. It will make a looser cast on and allow you to start knitting easily.
Another thing that might have happened is that you were casting on on the tip, possibly? That would make your stitches too tight. When you cast on, don't pull the stitches tight--just snug them up enough to keep them even.
You'll get it.