香港有沒有和自我防衛有關的法例?

Not directly.

In Hong Kong, there is no statutory right to defend. However, a right to defend is recognized as common law based on the circumstance.

Also - indirectly, the use of force is authorized by Section 101A of Criminal Procedure Ordinance (Hong Kong Ordinance Cap. 221) to arrest any suspects (by defending yourself, you are also stopping crimes at the same time).