I have a baby panther cham right now and saw him scratching his eyes and moving them all around in his head and got really scared.
I did some research...they move there eyes in there head to clean them, especially when its raining. I had also introduced a new uvb light. Baby chams especially, have fragile eyes and need proper vit.A and uvb. After 2 days, no more sctratching.
As your cham is keeping it closed, maybe it needs a new uvb as they burn out. Or it could have something stuck in there and wont open it.
If it is a new setting somehow maybe it doesnt like the light, but just being 1 eye, prob more on the something stuck or dificiency.
Good luck!