Hello Aquarius28, welcome to the Forums, although I am sorry for the somewhat worrying circumstances!
It is difficult to diagnose exactly what the issue may be with your cockatiel, and unfortunately we are not an online avian veterinarian service. The following link may help you to locate one in your area however...
My little lorikeet had something rather similar a while ago on her lower eyelid, and her vet prescribed her a painkiller and anti-inflammatory for treatment and she made a full recovery. It is best to have it checked out by an avian health professional if you possibly can, to rule out anything more serious. I am hoping that your cockatiel's issue is similar to my lorikeet's and that it can be assessed and treated by an avian vet.
Wishing your little one all the very best for a full recovery, and hope that you will keep us posted!