Not an Emergency, but it is an unknown injury

[nuthatched]

Yep, I've seen it on my friends chickens before, put some Vaseline on it. Check this reddit page for the cure:

https://www.reddit.com/r/BackYardChickens/comments/180uj20/bumble_foot_treatment

The first comment on that thread a has the right method. The infection must be removed first.
https://www.backyardchickens.com/articles/treating-bumblefoot-a-simple-surgical-approach.75146/