Does GDPR apply to a hobby Telegram group admin? England

I applied to join a closed Telegram chat. The chat is for a local group of people who share an interest. The person who runs the telegram chat also organises social gatherings and has a website. They also run free to attend events with a limited number of free tickets and the option to "pay what you want" which I presume goes towards the running of these events. I have not previously attended any of their events.

When applying to join the Telegram chat the admin, without my permission, managed to find some information about me on unrelated social media and used this to question me in order to confirm I am who I say I am, something I am uncomfortable with. I have since been more careful about what information about me is available on social media and am no longer going to join the group or attend any events.

Does GDPR apply in this situation? I do not know if the person has saved any information about me but I would like them to confirm that they have not or ask that they delete any information they have of me.

Thanks