Accidently licensing a photo I didn't want.

There is no way to unlicense. What is the asset ID? If it did cost more than 1 credit, you confirmed your purchase. You may try to contact Adobe customer care for a solution into this. If you have a teams account or an Enterprise account, you need to contact your administrator to do that. If you have an individual account you can contact customer service as shown below.

Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers need to be disabled, you need to accept cookies! If the chat window fails to open, or is non-responsive, use a different device and/or browser to start the interaction.
Support phone numbers may be found here: https://helpx.adobe.com/contact/phone.html. Kindly note that phone charges may apply.

For support via Twitter:
https://twitter.com/AdobeCare

(see also here: https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 or here
https://community.adobe.com/t5/account-payment-plan/how-to-contact-adobe-support/td-p/11843852)



Important: Adobe does NOT contact you unsolicited by e-mail or direct message. If you get contacted by direct message from a person, claiming to be an Adobe employee, look at that profile and look, if they bear the “Adobe Employee” marking under their name. Adobe support does not use Skype to give you support.


If in doubt, ask the forum.