Stoping Unwanted iCloud Use

Turned on my Mac Pro a few minutes ago and I got the following message.

" Your Apple ID and phone number are now being used for iCloud on a new iPhone. " ( my iPhone is not new. )

" If you recently signed into "xxxxx iPhone" you can ignore this notification."

On the bottom of this pop-up window is an "OK" button. Well it's NOT "OK" what should I do?

I have made no changes to my iPhone whatsoever. Just normal use today. In my iPhone iCloud settings everything is turned off except sharing Contacts and Find my iPhone.

Any ideas why I received this message on my Mac today ?