Good Morning,

Have you looked at the underside of the leaves to see if there are any bugs?  You may have to scrape the area because somethimes you can't tell if they are bugs.  If you see no bugs it may be Oak leaf blister or Taphrina blister, caused by the fungus Taphrina caerulescens is a common disease affecting many species of oaks. Members of the red oak group are particularly susceptible to infection.  Disease development is favored by cool, wet springs
and, in years when such conditions occur, noticeable leaf deformity results. White oaks are rarely infected, even in years with cool, wet springs. Heavy infections of red oaks impair their appearance but do not endanger the tree health.

I hope this helps.  Thanks for using our service.

What are these ugly bumps on my tree’s leaves? - MSU Extension

What's wrong with my plant? : Garden : University of Minnesota Extension (umn.edu)