Have you tried to renew the domain?
It sounds like your domain would be in its grace period and you should still be able to renew it.
For most TLDs registered through WordPress.com, an expired domain falls into a grace period for about 10 days to two weeks. During this short window, the domain can be renewed at the regular price. If you experience difficulty renewing your domain during this time, go to the Help section. There will be a link to contact Support for further assistance.
If you are still having trouble renewing your domain, you can add the modlook tag to this thread and a staff member will be able to assist you.
Learn more about getting a moderator/staff reply for your questions: