If I understand your question, you’re asking why your pin is on .co.uk, when you uploaded it to .com?
Pinterest has a network of servers across the world, which for as long as I’ve used it, have had localised IDs. Ideally, your pin is distributed to as many of them as possible. Pinterest will pick up pins it likes and distribute them (I believe that’s how the central thread is created). It’s a good sign, I’d say.
I should add, this is complete guess work from personal use over the years.