My glider has been biting for a while and always goes through the skin and my finger has been red and painful. Could it be an infection or something?

If he's biting, you may want to give him more space, and time.

As far as an injury to you, I would treat it as an infection. Especially if it's an old bite.

Okay, I see he's a single glider. I'm not sure how long you've had him, but he's probably scared.

My glider #2 was a biter. It took over 4 months to get her to stop. Getting him a buddy might help. Try feeding him treats through the cage and maybe give him a licky treat of honey or yogurt from your finger through the cage. It may take awhile, but you have to earn their trust, he might still think yo may want to eat him. Check out bonding (just click on the blue word). There is a lot of great advise. Please keep us posted.

oh yea, I might have forgot to add, they don't usually like to be held in your hands when they are full awake, they want to run, jump and play...

Since he is a single glider, he will require a lot of your time, and toys and a check out glider safe wheels too.