I had surgery on Friday, I noted a swollen lip how could this injury have occurred?

I had surgery (48 hours ago) under general anesthesia. In the recovery room, I noted a swollen lip, in one specific spot like an injury, but no broken skin like I had bitten it, and my lip still hurts quite a bit. Surgery was no where near involving my mouth or face area. The nurse in recovery room noted it, but didn’t seem to think much of it, other than to say it probably happened during anesthesia, which confused me a little. How could this injury have occurred? What can I do for it?