Stupid Newbie question regarding UK tax. (need help, kinda freaking out here)

So basically I know nothing about crypto.

Me and a pal was goofing around and I bought £10.50 worth of etherium as a joke.

However I quickly learned this shit is taxable. I sold it within 20 minutes at £9.90.

To you guys it seems like a stupid question, but to me (an 18yo with no real knowledge of crypto) I'm kinda freaking out if I have to pay tax for selling it.

Or do I at least have to report it?

I'm not active in the crypto community, and I know nothing about it. I did a dumb thing now I'm panicking.