Bundle branch block usually causes no symptoms. Right bundle branch block is not serious in itself and may occur in apparently healthy people. An incomplete RBBB just means the electrical signal is not completely blocked. However, it may also indicate significant heart damage due to, for example, a previous heart attack. Left bundle branch block tends to be more serious. In older people, it often indicates coronary artery disease due to high blood pressure or atherosclerosis.
I have one myself, 50 years old and was told by my cardiologist not to worry about it without symptoms.
Hope this helps.