This is a common complaint for people who grow weeping Japanese Maples where heavy snowfall or ice is a problem. These trees should be pruned with snow or ice load in mind to prevent splitting in the first place. You don't want the branches to catch more weight than they can hold.
We need a picture to determine the damage on whether it will 'heal' or not.
I have cut off the weaker side and shortened he other side with the idea to eventually remove it also as the lower branches gain height. It all depends on the length and location of the split.
Either way, it's a big setback.
Mike

Thanks; the split in the trunk is horizontal about 1/2 way through the diameter. I have the tree trunk lightly wrapped with gardening cord and staked up so that there isn't a lot of space between the two parts of the trunk. I'm kind of hoping the trunk will scar over but also sense that it might be too difficult for nutrients to travel up the trunk.

Even if it heals, it will split again until you fix the problem of why it split in the first place. Remove or drastically shorten the offending branch.
Mike

Thank you. It's still small and in balance. It's in a tiny front garden on a city block. So, I think we were the offenders by allowing some of the extra of this year's massive NE snowfall to be shoveled on top of it. Very dumb on our part and will think about some sort of chicken wire barrier if it survives to next winter.

It happens. don't beat yourself up. you all had quite the snowfall this year.