Sometimes other birds will peck at a wound on one hen, so separate this bird from the others for a few days. Then, you could try sterilizing a needle and using that to lance it, then clean it out with disinfectant designed for animals and let it drain. She'll just wipe ointments off on her body feathers and dirty it again. Is the hen eating and drinking normally? What do you mean "some distress " ? Can you be more specific?