Consider it recycling. When you took the pic, you were thinking of yourself. But when you looked back at it, you were reminded of a love interest. The image now has an added layer of meaning.
And also, I believe it’s cool if you communicate this too. Just say it’s not a real time pic (it’s not Snapchat), that you took it for yourself a while back and that you now want to share it, for whatever reasons. If the other person doesn’t trust you on this, and chooses to believe you took this pic for another person at a different time and is angry because of this, don’t bother sexting again.
I once got into a misunderstanding for not communicating this properly. I sent a flirty pic showing daylight during nighttime, like if I had a tele-transportation machine or something, that weirded out my boyfriend. Silly me.