I handed in my resignation letter due to being ill after getting knocked down by a car. I received 2 messages from 2 of my work colleagues stating that my manager had read out my resignation letter to the rest of my work shift, around 15-20 people.

The resignation letter is confidential in itself however my resignation letter contained some information about my health and the incident that occurred for me to stop working, clearly my manager as breached my confidentiality, what should I do and how should I go about it?