Use Google Images to find the original source of an image , Google allow you to upload that image and search similar image sources where that image is published , in this way you can find any image orginal path or source as well as you can find and track where you image is published in all over internet.
Same you can use to find your pinterest photo , In Pinterest, right click on the photo. Select “Copy Photo URL”.In Google Images, click on the camera icon. Paste photo URL and click “search”. Locate the original source from the results.