Others will probably tell you MUCH different advice than me, but I say go ahead and open it up. But...since you are new here you might not realize that I dry hatch, which means I add ZERO humidity. Not a drop. Do my eggs hatch? Sometimes yes, sometimes no. Do eggs hatch with proper humidity? Sometimes yes, sometimes no. So I tell you to open the bator and do what you need to because I am not a worrier over humidity.
Also...if eggs have pipped but made no progress in a day, I go in after them. All the popular wisdom says not to, but I do anyway.
If the chick is not moving at all or making scratching or peeping sounds, it's likley dead. I'd still carefully check it out anyway. Here are some rough guidelines, incase you are interested (these are mine, others differ).
Enter the egg from the FAT end. Crack a small area with something and then carefully pick a small hole. Do not act as if you are peeling a hardboiled egg. This is a bit more delicate than that.
You should see a dry, white membrane covering the chick. Like paper. If the fat end is full of liquid or goop, your chick has most likely drowned. (drowning was my number one cause of chick death, thus my move to zero humidity). You can slowly break away the egg until you get to the membrane. Then you need to tear the membrane VERY SLOWLY and only a very tiny tear. If it bleeds, apply pressure. Gentle finger pressure. It does not take much blood loss to kill the chick. That blood is supposed to end up inside him by the time it hatches and if there is still lots of blood in the membrane, the chick is not quite baked. If there is little or no blood in the membrane, he is closer to being hatch ready.
If lots of blood, set egg back in bator. Now that the egg is open it is more prone to drying out and at some later time you will likely have to dab water on the membrane if the chicks breaks through and gets stuck.
What I normally do is break away fat end shell, open membrane and carefully peel back enough membrane to see what's going on. Then I will try to get the chick's head out of the shell while leaving his lower body inside the shell. If the chick is going to live, this gives him a chance to kick himself out. Chicks that are too pooped to even kick free of the lower half are usually too weak to live. Usually, not always.
It IS possible to pull the chick all the way out of the egg BUT (and this is a biggy) only pull a chick out if you can determine that all his yolk sac has been absorbed into his abdomen. If you peek around in that egg with the chick still in there and see anything that looks like a veiny egg yolk, LEAVE THE CHICK IN THE EGG! Weak chicks with a closed up abdomen sometimes make it. But chicks with their yolk sac still out almost always die. Leaving him half in the shell lets him breath, removes SOME of the battle of hatching, but allows that yolk sac more time to absorb into the gut.
This is information overload. Go ahead and add your humidity. Like I"ve said before , do not fear the bator, no matter what the book says. It's an incubator, not a bomb.