Sorry, I can't find what I was looking for. You might prefer to frog rather than cut the sock above the toe, knit some rounds on the foot and then graft it all together. I can't think what to search on right now. At least your cast on isn't too tight. That would be awful.
ETA I just realized...you don't need to add rounds you need to subtract them so you'd remove some and then graft together. Sorry 'bout that.
Happiness is catching that dropped stitch while it's still fixable..