Without meaning any sarcasm, it's great that you have a working immune system. I hope it keeps working as well as it has for you to trust it so much.
You're being asked to wear a mask for those that don't have good immunity such as you do. Also for those that are at greater risk, even if their immune system is working ok. The statistics behind deaths are there for you to review.
Saying "your immune system is not my concern" is, pardon the harshness, selfish and somewhat childish. You're saying that you won't go through the smallest of inconveniences to save someone else's life.