Thank you for contacting Ask Extension. Your Locust appears to be suffering from what we call winter cracking or frost cracking in trees. What happens during very cold weather is that the side of the tree, usually south facing has temperature changes that are more pronounced than on the rest of the tree. The freezing and thawing of the bark and side of the tree facing that sunny area during the day, but re-freezing overall or at night, will lead to cracking of the bark. Often the tree can heal or compensate for the crack in the bark on that side. It can tend to re-split under the right conditions. There is nothing to be done at this time but you will want to watch that area closely for signs of insect damage or disease as time progresses. Do not paint or cover the area. The tree should begin to form a callus or thickened area around the split during the growing season. Avoid fertilizing trees in the late fall, as that encourages new growth and new growth is more susceptible to splitting. Thin barked trees are more prone to frost cracking. Keep the tree watered next summer if we experience times of drought, and water once a week, deeply. Because of where the crack is located, it might be at a higher risk for limb failure, and should be looked at my an arborist to determine that.

If you are worried about the general health of your tree, consider having a certified arborist give you an evaluation. Be sure to always hire an insured, tree care professional, preferably and ISA Certified Arborist with the experience, expertise, and equipment to provide proper tree care. Require proof of liability insurance to protect yourself as well.

I have included some references for more information:

https://hortnews.extension.iastate.edu/shedding-peeling-and-splitting-bark-shade-trees

https://www.canr.msu.edu/news/frost_cracks_in_trees

https://www.arborday.org/trees/health/arborist.cfm

You are welcome!