Here is a diagram of the location of air sacs in birds, and chickens are similar. Any bumping or trauma can cause a leaking or ruptured air sac. I would just watch it, and hopefully, there won’t be a need to needle it. If you have the time, it would be good to shop for a few 10 ml syringes with...
How is the chick acting? Is he breathing okay or struggling? If he is not in any danger, I would leave it alone, and it should be re-absorded by the body. If he is having problems breathing, or it gets very large, you can stick a sterilized needle into the bubble and push out or withdraw the air...