Okay iguanas are known to eat lots of fruits in the wild but due to the fact that you have one as a house pet may be a lil troublesome. I raised lots of iguanas over the years and let me tell you its alot of work. That bump on its back is called mbd.
Metabolic Bone Disease. This happens when a reptail doesnt get plenty of calcium in its body. Theres only three ways to take care of this before it gets worse. One buy calcium in powder. Two buy a uvb light for it. Three now this my sound weird but trust me it'll work. Get some lidoderm lidocaine patches. This is something you get from you doctors. These patches help with pinched nerves, painful joints, and relieves pain. Like i said before you get these patches from your medical doctor. Not a vet. After getting these patches, cut it in small pieces and apply to the spot where the mbd is showing. I hope this message helps you and many others with the same problem.
I'm just talking about the other cases. In your case, it was the diet. OHH MAN lettuce?? Its like water.
