My 8 y/o, who has a slight learning delay recently began to cross his fingers. He will walk around like this all day. Should I be concerned?

Yes but don't panic. Obsessional behaviors like this can be an early indicator of more serious mental health or developmental problems. However, this might be just a harmless blip in his behavior. Take him to his pediatrician and ask him or her what s'he thinks. Meanwhile, just be alert & observant. Best wishes.