Nothing you can do really, except cull, or watch the peep be anemic from lack of food, if it is extreme enough it will starve...or will be small and never truly develop..mother nature can be cruel it seems, but that's my experience and my opinion as what's best..good luck.
At 3 weeks old your bird's case is probably borderline. The earlier the malformation shows up the more extreme it is because it continues to progress until the bird reaches its full skeletal growth (16-18 weeks give or take). Some birds are mildly afflicted and can live a normal life with just slight alterations in their environment- deep feed and water dishes, beak trimming and filing as needed. Some birds are so afflicted that they should be culled ASAP because there is no way outside of regular tube feedings that they will survive. Without tube feeding these birds slowly starve to death.
A pic would help to see how extreme this bird's problem is. You can trim and file the beak as needed to help get the most use out of what it has, but this is not going to be enough if the case is too extreme. The question then becomes- how much time do you have to dedicate to this bird?
I trimmed the beak and will give it some time to see how it does. If it seems to be failing I will cull it. :- ( I will send some pics if I can find the cord to connect my phone and computer. Right now the bottom beak does not seem too bad, but we will see. She didn't like the trimming eve though it didn't bleed. Maybe I should file the beak some too.
BTW, your avatar is great. Bet there is a great story there.
I can tell she is in pain. I read trimming a beak was like clipping toenails, but it surely wasn't. She is hunched over and ducking her head behind her wing, or just hanging her head. She isn't active. I kind of wished I hadn't clipped the beak, but I guess if it helps it will be worth it. If it doesn't help and I just end up culling her, I will feel bad that I made part of her short life miserable. I hope she feels better in the morning.
Morning is here and she does seem to feel some better. I was hoping she would be all the way better. I made the chicks a soft mash of their starter pellets with water and yogurt. They all seem to be liking it including my little "special needs" chick. However, the other chicks occasionally peck at her beak. Do they think the lower sideways beak is food they are trying to get. This could be a problem that I will keep an eye on. Maybe that is also why she has taken to facing the wall of the brooder.
A mash is a better feed source for her because she should be able to keep more of it in her mouth and get it down. She is going to be a messy eater regardless, so the other birds are going to be picking at the bits of food debris that ends up all over her. They have also noticed her difference and will continue to explore it by pecking at it. As long as she doesn't shy away from them and instead gets up in their faces when they pick at her, she will be fine. If she is shy and withdrawn, then she is not going to have a good time in a flock.
Thanks. You have been a great source of information. She seems back to normal behavior. I think the mash really picked her up. She ate and ate and ate. She must have been pretty hungry. Still looking for the cable so I can down load a picture of her.