This is not a hickory tree. Hickories have compound leaves.  This tree does not. It appears to be Hackberry or Celtis oxidentalis.  They are prone to a number of galls.  These galls do not damage the tree except cosmetically. This is going to be something that you can ignore because these galls are not hurting the tree.  With a humid summer, the tiny gall-making insects have had a really busy year.  It is difficult to spray for these because the spray has to be applied before any galls are made.