Please post a link to the pattern if possible when asking questions because it helps us help you.
You will probably have to frog (rip it) back and start over unfortunately. It can be a pattern breaker to use a different weight yarn and needles. For instance if the pattern calls for sport weight yarn and you use worsted it'll be a lot bigger. What weight (sport, DK, worsted, etc) and needles did the pattern call for and what did you use?
What they are suggesting as far as pulling the cable out is doing a modified magic loop method. I prefer to use two circular needles or double pointed needles myself.