Google Play Music Icon Is Incorrect
A simple, although superficial, solution would be to manually change the cover cover image (download it using a web browser and set it as the album cover). The following link has instructions on how to edit metadata and album art.
https://support.google.com/googleplay/answer/1100174?hl=en

If the problem persists with other songs in the future, you could try using a file managing app to solve the issue by searching for and deleting the image you are seeing (might be a leftover thumbnail somewhere or in the Google Play Music folder).