Contact them privately.
If you genuinely think that they might not realise you don’t want it online, think about getting in touch with the person directly.
They may not know that what they posted is making you uncomfortable.
Stay calm and say you would prefer it if they take it down. Let them know that it might not be a huge deal but you also don’t want it to become that way.
If you have been tagged in the picture or comment, remove the tag. On Facebook, change your settings so that you cannot be tagged without approving it first.
Try not to panic
If you are feeling like it is low key, the person who posted it probably did not post it with the intention to cause you harm, so approaching it with a calm attitude may help the situation.
Let them know that you would like the post/photo taken down so that other people don’t see it.
If you over react and become all angry and upset at the person who posted it when they didn’t mean to hurt you, then they could feel like things have been blown out of proportion.
Chat to a friend about it
Get in touch with a friend whose opinion who value and trust.
Give them the rundown on what has happened and see what they think?
You might find their perspective helpful so you can see things objectively and you might be happy to just let it go.