My baby boy had an abscess about a year an a half ago. The whole side of his face was swollen, and his eye was bulging out of his head. Took him to the vet and they drained it. I had to reopen the cut every night and drain what had accumulated in it. After that, I would put an antibiotic solution on the cut and try to get it into the whole that the abscess made in his face.
My advice is to just keep opening the cut every night and drain it. I think I had to do this at least a week before it stopped filling up. I was then able to stop and it healed up. However, after a month or so, another abscess popped up and I had to do the whole process over again. It is not an easy process, physically and emotionally (for both you and your glider), but it is better than having it fill back up and having to get him cut open again to release the pressure.
Before trying to get the cut open, put a warm washcloth over the cut to soften it. After a few minutes, try to gently pry the cut open. Apply the washcloth again if it is not opening. (Try to do this twice a day. It will be easier to open when it comes time to drain it.) Once you get the cut open, squeeze the abscess and drain it as good as you can.
This was agonizing for me to do to him. I know it hurt, but it needs to be done. Try not to show your feelings, your glider will pick up on them. Also, make sure you take your glider out as often as possible so that he doesn't associate you with the pain. Try to make it a routine. Like in the morning and at night. Give your glider lots of love the rest of the day.
I am not familiar with the medication your glider is on, but ask the vet if he can give you an antibiotic to put in the cut. Like an antibiotic eye drop. That seemed to work well with my glider.
I really hope this helps you and your baby. If you have any questions or concerns, I will do my best to help you:)