first thing I would do is take a 3cc syringe with a 22 gage needle and draw fluid out of the cyst and see what your dealing here is the fluid clear or is there infection or blood don't lance it yet . insert the needle in the lowest point of n the cyst be sure you go into the cyst this does the least amount of damage to the tissue and doesn't leave a open wound If the fluid is clear I would draw as much as you can out if the fluid blood red do the same thing. and just watch it checking daily If you find puss or infection you will need to flush it . at this time lance the cyst as low as you can try to keep it small just large enough to drain take the syringe and needle use hydrogen peroxide and flush the wound apply antibacterial ointment any kind you have will do. start the chick on a antibiotic I use DURVET duramycin-10 soluble power 1/4 teaspoon per qt. clean water or until it looks like lime Gatorade treat for 5 to 7 days I get mine at or local farmers Co op or TSC I give this to all my chicks when they leave our kitchen and go into the brooder shed at 7 days old just as a precaution .if you keep chickens its a good thing to have on hand but like all meds for chickens is dosed for a 100 birds a cyst is a puzzle hard to figure why its there and what caused it good luck with your chick
