In that case, I would probably watch but not do anything at present. Since it did empty itself yesterday, that might be a sign that it does not need treatment.
@Eggcessive do you have any better ideas for this chick?
Are you sure that contains air?
In the photo, it looks to me like a perfectly normal chick with a crop full of feed.
Do you have other chicks? If so, I suggest looking at the chest area of each of them, and feeling the crop of each one, to get a better idea of what is normal. Then if this one...