You definitely don't want your nocks too tight. When you hang them on your string, a light tap on the string should make them come off.
I'll say again, you need to have a nock tied under your arrow. Your problem initially was that your arrow was sliding down the string when you released. That makes the arrow bounce off the shelf and gives you horrible flight. If you don't have a second nock, you'll need to have your nocks too tight to keep them from sliding. That's not good, either. With nocks too tight, tuning your broadheads will be difficult, and bareshafting will be a nightmare. Your fletched arrows might look like they are flying correctly, but odds are they aren't.
You will get your best flight from correct nock tension and a double nock. Just try it. It takes about 30 seconds to tie one on.