Boss sent my naked photo on Slack after relationship and then deleted it... How bad is it?

tl;dr: I had a (mostly) consensual relationship with the CEO of my company (and my boss), during which time I text him a half naked photo of myself. After we ended it and he said he deleted everything from our texts, he messaged it to me on Slack. He deleted it shortly thereafter, but... still seems like a big deal, no?

Ok, here's the long story...

I joined the company last January. In March, my boss (the CEO / founder) started sexually harassing me. I'm not proud of this at all, but it's a great job and last August, I just kind of, gave in. It started as texting, but then he intentionally got a hotel room a few doors down from mine when we went to a trade show, where it then turned sexual.

Again, I was not at the time and am not proud of it now.

He called and text me constantly – like 5am to 7/8pm, Monday through Friday, and would call me, and extend our 1:1 to like 90 minutes from 30 minutes.

I feel like I just got sucked into the whole thing, but I would consider myself a consenting adult (outside of the massive power imbalance).

He loved to dirty talk and sent me dozens of pictures of himself touching himself. Eventually, I sent him one photo of myself topless, where you can see one of my nipples, but not my full face.

We ended things a few weeks ago and he told me he deleted everything from his phone.

This past weekend, he sent that photo to me via Slack. I told him to delete it immediately, to delete it from everywhere, and that I couldn't believe he would send it on a work app, of all places. He apologized. Said he opened an old laptop and saw it and was thinking about us.

I just... I realize there is a power imbalance to the entire thing, but... how big of a deal is this? I'm low key freaking out about it and just need to know if there is something else I should be doing?

I just keep thinking about my naked picture on a work server somewhere...