With such a large pip hole but no real zipping yet, I'd be concerned that it can't turn to zip and is stuck. I just had to rescue one of mine that was like this the other day. It was beyond ready to hatch but couldn't. Definitely chip away some shell from where the hole is. If the membrane is brown underneath, it needs help out.
Kind of hard to describe exactly how to open a shell carefully. I've helped my eggs hatch many, many times (but I use a broody momma and sometimes can't tell if the egg is just behind or if it's having a problem). Either way, even if I opened one a little too soon, I was careful enough that any vein I hit was very minimal and wouldn't cause much bleeding. Then I'd leave them and they'd hatch out fine.