While grocery shopping, I saw that a photo of me from today had been posted.

This is a story to read when you discover that someone photographed you today while you were grocery shopping and posted it online.

Scenes

While grocery shopping, you saw that a photo of you from today had been posted. — As I was heading to the checkout with my basket, I saw a photo of me from today posted by an account I didn’t recognize.
It felt like deleting and blocking would make it all go away. — Your hand reaches to delete the post and block the account first. But there’s something you need to preserve before that.
What needs to stay with the photo — The photo seen inside the supermarket included the account name, the posting time, and the accompanying text. Closing the screen breaks that trail.
The context matters more than a single piece of evidence. — If you save only the photo, you may lose who posted it and when. Save the account, time, and accompanying text as they appeared on the original screen so the order of events remains clear.
Before deleting it, save the screen once. — Don’t delete the new screen right away. Save it once with the account name and time visible. You can close the screen afterward.
The first image you save opens the next door. — Keeping that day’s screen gives you a place to look back later and see what followed. Today, it’s enough to remember just one image from before you delete it.