If a celiac artery is knicked during a laparoscopic abdominal surgery & surgery is converted to open to repair it, could you quickly bleed out? is that risky?

Depends on hole size: That would, of course, depend on the size of the opening in the artery, and the general health of the patient. A healthy patient has normal blood pressure and thus can squirt out a lot of blood through a hole in a medium-sized artery. So, there is no way to answer this question with anything other than "yes." That's because it "could" happen.