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.