There's no medical evidence that says that guava seeds can cause appendicitis however it is possible that some non-digested food, like a seed including the guava seeds, could block the opening of the appendix, at least in some cases, and start the process of appendicitis.
However most times it's something else that causes a blockage in the lining of the appendix that results in infection which then causes bacteria to grow and rapidly multiply which then results in the appendix becoming swollen and inflamed which then leads to a burst appendix if not treated in a timely manner.