I cut my to. how do i know if i need stitches or not?

Depends: That would depend on the depth of the wound. Important points - depending on what you cut it with you may need a tetanus shot (unless you are upto date), you also have to make sure you didn;t cut any tendons, so make sure you have good motion of the digit, loook out for signs of infection. If bleeding stops easy, apply an antibiotic i.E Bacitracin and a bandaid.

Stitches: May need stitches if wound depth > 1/4”, wound edges are gaping or jagged or if fat / muscle is visibly extending from wound. See: http://www.mayoclinic.org/first-aid/first-aid-cuts/basics/art-20056711