It is not a UV bulb problem. It is a simple thermal burn, a halogen bulb puts out a hell of a lot more heat ofr its wattage than a regular incandescent bulb. I could show a pic of my melleri with over an inch of his back gone from burns. And that was a 90W halogen bulb nearly a foot away from his baskign spot. The most common halogen bulbs are spotlights or flood lights, which also focus the beam a bit, extending the burn range.
Get the bulbs out of the cage, and make sure the chameleon cannot possily put itself in a position to burn itself further. If you can put your hand anywhere int he cage and feel too hot, it's too close. I reccomend ditchig the halogen, personally.
Also, 10.0 bulbs are NOT too strong. If you have a screen cage, simply lift it off the cage a bit. At worst, the light will simply last longer than a 5.0 will. I just did some readings on a 1.5 year old 10.0 and a new 5.0. The 10.0 was putting out more UVB at a longer distance. To me, 5.0's are a waste of money for that reason alone.
You will see eye problems if they are too close to the uvb bulb. They dont' put out enough power to burn them.
Another bit of opinion. Take him to a vet, but just get topical medication. If he has no infection, he has no reason to get general antibiotics. For these things, preventative medicine will almost invariably cause more harm than good. I've screwed up more than most people, simply because everyone screws up, and I've kept these things longer than most people.
I've had way more burned chameleons than I would admit, if I were concerned about my pride and not education and information! Never have I seen a burn require general antibiotics. A good application of Silvadine tot he affected area has always been 100% successful for me. And If you saw the quantities of chameleon flesh and bone lost from bunrns, you would be amazed. My melleri has lost enough meat and bone from his back to make 2 pygmy chameleons. MY old male veiled got so badly burned one time, his knee was cooked to the bone, and the connective tissue destroyed. His skin healed around it, and he had a permanantly dislocated knee for the rest of his life. The burn was so bad, 100% of his skin was gone - the ribs were exposed in an area larger than the size of a quarter.
I gave that male veiled baytril - as a preventative, form my vet - and he stopped eating and stayed on the ground for two days. I stopped, and the next day, he was back to normal. Never even let it on that he was hurt.
These things recover from superficial damage in a way us mammals cannot relate to!
Go to the vet, get some silvadine (and get a lot - it will come in handy with any an dall surface wounds), and reduce your wattage. Pull the lights out of the cage, too.
He will be fine. You will most likely not notice a change in his behavior - despite the fact that he is most likely going to lose all of the areas that are black on his dorsal crest. They'll probably fall off over the next 6 months. The skin on his side may scab up into thick, nasty scabs, which may fall off and re-scab up.
Just keep it rinsed wiht an antiseptic (chlorohexadine is good) and covered with silvadine (developed FOR burn patients, in fact) , and he should be fine.
It is my OPINION (and I am not a vet) that the last thing he needs is a preventative antibiotic. If he's got an infection, different story.
Here's a good selection of pics showing the burn, right after it happened, before it scabbed up.
Pics are big, so I linked to them.
http://www.zorabellarose.com/Chameleonpics/burn.JPG
And after it started to heal.
http://www.zorabellarose.com/Chameleonpics/Ascar.JPG
http://www.zorabellarose.com/Chameleonpics2/IMG_1810.JPG
The infamous snapping the chameleon's neck" pic (I had to hold him somehow - he was in the sun, and he got EVIL in the sun.)
This pic was to show the regenerative abilities of chameleons. Not only had the destroyed skin healed (it was entirely gone in the area affected), but the pigment started to come back. When he was older, the skin had almost completely healed up over the scar tissue, color and all.
http://www.zorabellarose.com/Chameleonpics2/IMG_1820.JPG