Sharing- How To UnShare?

[lickerice4u]

Yesterday I somehow must have hit the share button next to Follow button beneath screen. I ended up with a small box labeled share. It acts like a mirror image with sound was created. I closed the original, but the sound kept coming from closed tab? and small share box remained. I have shut down my computer overnight, but when restarted tab with share box reappeared with sound.
How do I permanently get rid of this share box? Dave