One of my chicks has a constriction on their leg.

[jennajane]

I just got my first flock of chickens last weekend (about 35). They were mostly born on May 8th and are a mix of mostly Chanteclers with a few Silkies and Ameraucanas. I noticed on little black chick not being able to move around so well. Upon closer inspection yesterday I noticed a constriction around his leg and knarly bit at on spot. It looks superficially like something is wrapped around it and the skin is growing over it. With each day he seems to be getting worse. Does anyone have any ideas of what it is, where I can start looking for information etc.?

Thanks,
Jenna