Is this just damage or is it an infestation of something? Will it repair itself?
Damage on Trunk of Lime Tree
Certified GKH Gardening Expert
It is difficult to tell. Check the tree for any other problems (on the leaves/branches/fruit)- if there are other problems, it is more likely that this is an infestation of a disease. See if it matches the symptoms of any of the diseases discussed in these articles:
You may also need to consult a local expert, like an arborist or local extension agent.