My rule of thumb if you're going to play doctor is "First, do no harm".
Since just opening the incubator can shrink-wrap everything inside that's pipped I don't like to open the incubator for at least two days after the first egg pips, longer when incubating waterfowl. The more eggs you are incubating the more chicks you put at risk when you intervene. And the majority of potential problems can be avoided by monitoringtthe hatch and making sure your eggs are losing enough weight. It's not always going to make things worse if you open the incubator, but there's no reason to interfere with the hatch unless you're certain there's a problem.
If you do decide to go in, don't do it out of ignorance. Read up on hatching and know what to expect. That way you know what's normal. For example, if your chick looks like it's peeping but you can't hear it, it hasn't lost its voice. It's absorbing the yolksac and really, really is not ready to hatch. Just because you think it looks distressed doesn't mean anything is wrong.
If you're sure you know what's wrong and you can do something about it, then you can intervene without opening yourself up to helper's remorse. First, you need to safely open the incubator. That requires that you have a plan for which egg you're going to work with and what you're going to do. Have all your instruments and supplies handy and a worksurface ready before you open the incubator. Whatever instruments you're planning on using, you should practice with them before you use them seriously.
If you can raise the humidity in your incubator without opening it bump it five percent and the take out the one egg you're going to assist. Only work on one at a time. Even an egg in trouble is in less trouble in the incubator than it is cooling outside it. Put the egg on on a padded, stable surface where it can't roll. A warm wet towel is good, a dry towel on a decent sized table or a good amount of floor space works too. I mention the floor as an option because you can't drop it if you're working there. Wherever you're working make sure it's well lighted and well heated.
Fix what you can and return the chick or egg to the incubator. Toss in a wet paper towel too. Let the temperature and humidity stabilize before working with another egg.