Help I posted a nude pic with my face on

I'm sorry to hear you're feeling worried.
This sounds like the sort of situation it would be best to talk over with a parent, or a trusted teacher - I know it might feel really embarrassing at first, but a teacher, for example, will have had safeguarding training, and will know how to help, or they can just provide an ear to listen

If the person who you sent the image to was / is an adult who pressured you into sending it, and you're worrying that they'll leak it because of threats they've made, then it - depending on the law in your country - will likely be a matter for the police, and a teacher or parent could help to deal with all that
This might sound worrying, but I think talking to a parent or teacher is the best bet

I was stupid when I was in 4th/5th grade. I chose to send it to them and they didn't pressure me at all. They basically did nothing illegal unless they leak it, then I have to talk to my parents, which would be so embarrassing. Is it very likely that the person who received my photo 2-3 years ago will recognize me if I happen to go by them?

You don't necessarily have to go to your parents - if you've a kind teacher, I'm sure they'd understand We all make mistakes, and plenty of people do silly things with the internet.

If the person didn't pressure you, perhaps they'd have immediately deleted the photo, or if they're a stranger, perhaps they wouldn't have opened your message at all. But, if you're concerned about it being leaked, then a brief bit of embarrassment talking to a parent or teacher is probably better than the embarrassment of it coming out. If the stranger is an adult, and in any way could be considered to have asked for the photo, or to have engaged improperly with you, then the police would likely have to be involved.

It's hard to know if they'd recognise you, but if they're a stranger you've no contact with, I think you're unlikely to pass them in the street.

By the way it didn't let me reply- I'm going to paste what I said in reply 4
It was a stranger. Just a site saying if you are in elementary and want to send me a nude pic come and I very stupidly did it. Is it likely that they will leak it?