Skinny is good!!! Thickened, fat or swollen limbs are a symptom of a few diseases/illness such as MBD (Metabolic Bone Disease) which is due to too little or too much calcium. Be happy for your skinny-legged boy!
Chams often do not eat fruit and veggies until they are older. Luna ate some tomatoes at about 5 months and then swore of them. I just recently got her back on (she is 2!). She will not eat thhe tip of a wooden skewer. Just barely stick it on the tip (if pushed too far on he may hurt his tongue). I find red to be a draw for her so starwberries and cherry tomatoes. She will also take bits of butternut squash but it is as if she forgets she likes it every few days so I place it on a skewer with something red and she gets it 
Don't be dismayed if he does not take to them right away, just try every few weeks. There are some fruits and veggies that should not be given in excess and some not at all and others you can feed daily. For a VERY comprehensive listing of the Calcium/phosphorus ration of LOTS of them and a coded chart on what is good and what is not go to the link below. it is geared for bearded dragons but the basic premise is the same for all. Have fun!
Nutrition
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0.1 Veiled - Luna
1.0 Beardie - Darwin
0.2 felines - Kyndra and Líta
1.0 African Clawed Frog - Skipper
0.3 Mad. Hissers (2 died ;(
0.1 Chilean Rose Hair Tarantula - Rosa Leigh
0.1 Goliath Bird-Eater Tarantula - Natasha
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