I agree with JPM about bark tracing. Dried, loose-hanging bark is an ideal location for pests to live and feed upon healthy tissues. If you can eliminate such a residence, then you may be eliminating further stresses. Also a clean 'wound' can decrease the time required for the tree to seal over the damage inflicted.
If the damage was caused by a lawn-mower, the bark tissue could have been possibly saved if caught early enough. Sometimes, and this is under ideal conditions, the bark can be gently folded back to its original location, secured with a few small nails and then taped in place with some flexible black electricians tape. Leave it alone for a few weeks to a months. Gently remove the tape and see if the previously damaged tissue has taken hold. If not, remove through bark tracing. Even if the procedure doesn't work, you can say that you tried. Also, the season makes a considerable difference. If the bark tissue is still 'slipping' due to the increased xylem sap flow of spring, your chances will be greater.
I understand that this will be too late now, but it will be in your mind, if such a incident should ever arise!