Worried about possible injury for my frog

[Sewing0916]

I noticed last night that my frog has been hiding behind the rock in his enclosure too often, and I thought he wasn't eating. Today I moved his rock around so he would be in the front of the cage, and he immediately started climbing the glass which made me think he had been stuck this whole time I thought he was hiding! I got a good look at him (even though he was dirty) and he looked so skinny! He seems okay now, he's been sitting in his water bowl looking at me. Should I be worried about him?

https://www.dropbox.com/s/2kud0kd9sz...81%29.jpg?dl=0

I can't get the picture to upload but hopefully this works