What is the treatment for a right bundle branch block? Is this serious?

None necessary. No treatment necessary and it is not serious unless other heart blocks or conditions are present.
Nothing. There is no treatment for this. It is caused by a delay in the electrical system of your heart. Usually it just happens, but it can be caused by a previous heart attack, so you should ask your doctor about that. If it just happened, no heart attack, don't worry too much. It won't really affect you very much.