Welcome to Shopify Community. My name is Olivia and I work here.
Thanks for sharing your question with us. First I want to make sure that you've properly updated your social media sharing image. In most themes, this can be done by:
Once that is updated, you may need to use debugger tools if an old image is still appearing.
If this is occurring on Facebook, use their developer tool to scrape the newest image at https://developers.facebook.com/tools/debug/. Insert your store URL at this link and click "debug."
On Twitter you can access a similar developer debugging tool at https://cards-dev.twitter.com/validator. Enter your site URL here and then click "preview card."
If this is happening on other social sharing sites, like Pinterest or LinkedIn, then make sure to check out this free online tool called Social Share Preview. You can enter your site link to check against all social media sites at the same time and also access unique debugger tools for each social media platform.