* Mfalme - This is the most common word for "king". It can be used for a prince if the context makes it clear that you are referring to a royal heir.
* Mwana wa mfalme - This literally means "son of the king" and would be a clear and accurate way to refer to a prince.
* Mkuu - This means "chief" or "leader" and can be used to refer to a prince, but it's less specific than the other options.
The best option will depend on the specific situation and how you want to emphasize the prince's role.