It appears that you have wild violet, possibly the native violet, growing in your lawn. It can spread through rhizomes or seeds and often has purple flowers, sometimes white or speckled. There are also yellow flowered native violets but they don't spread as quickly and rarely grow into lawns. Here is a great website from the University of Minnesota that talks about identifying and controlling them in lawns.

https://extension.umn.edu/weeds/wild-violet

Thank you soooooo much!!! 
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