I'm not an expert but I think if the wound doesn't stop bleeding after a few minutes of applied pressure, or the gap in the laceration is large enough that you need to literally pull it together then you should go to a doctor for stitches. I CAN say though that, there is a time limit before they will do stitches at all (higher risk of infection to stitch after that because the infection could get trapped inside the wound), so you should see a doctor as soon as possible if that is the case. In many instances, stitches are a manner or helping the skin align nicely and to avoid excessive scarring.