Drain the extra 2 qts. If you don't have any issues now, chances are you didn't do any damage, biggest issue would probably be a blown seal.
Mine had 26 qts in it due to the injector recall issue and I have had nothing arise from that. Quite a few Dmaxes have run with full crankcases due to the injector issue and a bad seal is the only issue I've heard of related to that. Others have listed potentials that could happen.
