Hello,

That looks like erythroid mite damage. The mites are very small and feed on the leaf causing the blistering or deformations you're seeing. There isn't anything you can do for tree to protect it against them. They are usually embedded in the plant tissue so getting pesticide on them is tough. There are many species of erythroid mite for many types of plants and most plants will tolerate the damage without issue. Environmental conditions are the biggest factor for mite development. If this becomes a reoccurring issue changing the localized conditions may help, like pruning the tree to open ventilation, or removing other plants to increase sun exposure. But likely nothing will have to be done.