My year-old son has 40 percent lung capacity, and Obstructive Sleep Apnea (OSA). For the last few weeks, he has been having this pain on his right side. Can someone tell me what it is, or what can cause this? I'm not getting any answers from his doctors.

I am not sure. I have OSA and I sometimes also get this pain. It could be nothing more than stiff or sore muscles in the chest wall.

If your sons doctors are not giving you answers its time to find a new doctor. There is no excuse for a doctor not to do anything about a child in pain.