Depends on the contents of underlying info. I don't think anything Jr was questioned on is classified, it's just shit he did on the campaign. He probably said the same shit to the press, "what he did in the meeting," etc.
Contempt of Congress is the only thing that comes to mind, and even that is pretty thin gruel.
Grand jury testimony is secret by law, but witnesses are free to tell the public what they tell a grand jury (classified info caveat, see narrow categories of classified info - ongoing investigation caveat, but not much in law to keep that secret - trade secret caveat but that is civil law)