How do I get my lawnmower started again?

I checked the oil and forgot to tighten the dipstick back on such that I got oil all over. I then drained it and wound up overfilling it such that the cord won't pull all the way. I took the spark plug out and I still can't pull the cord more than six inches or so... It was just running recently so I think this has to do with my oil "screw-ups" more than any filter. I haven't taken the carburetor off. Thanks for informed replies.