Your hen should be able to hatch the chick ok. Does it look like the chick actually pipped the egg. Sometimes a first time broody hen will peck the egg especially if things do not seem right to her. You rarely see a egg pip naturally at 18 days under a broody. I sent you a message about the emergency double boiler I used but I think I would still let the hen sit on the eggs.
Sometimes thing are just not right with an egg and the hen will usually know. No matter what we do, thing sometimes do not work out for every chick. It is really hard to accept but my advise to you is try to be prepared to let the hen do what comes naturally. With that being said, there are some bad moms and they for some reason do a terrible job of hatching. Keep a close eye on her and the other eggs and if there are anymore eggs with holes then you might intervene. Most hens will learn the knack of hatching and do a great job but some are just not good at it.
