Making mistakes

I knit my socks on two sets of needles and only have one set out at a time (I have cats, I can't have wool/needles lying around!) and it wasn't until I got both sets of knitting out that I could see that one was slightly bigger than the other. I was using a 3.0mm set of needles in bamboo compared to a 2.5mm set in steel! I have since bought a 3.0mm set of steel and will be taking the knitting back to the cuff to start again from there. Frustrating but worth getting right as these socks will be an Xmas present.