There shouldn't be any bumps. :think: It's possible that you did the carrying method incorrectly.
You can leave short floats without worrying about catching, especially if you use wool since they'll kind of felt to the back over time. Even with acrylic, the floats themselves can be short enough and snug enough not to be a problem, especially with a Christmas stocking since it only gets used once a year. :shrug:
You could get away with catching the yarn every inch or so. When you catch the yarn, insert the needle as if to knit; bring the yarn being carried up over the right tip from back to front (make sure it comes under the yarn in use); wrap the stitch with the yarn in use; remove the first yarn. This should catch without showing on the front.
It's hard to explain clearly how to do it--easier seen than said, I guess.
I don't think your bumps look bad, btw. A bit of texture.