You said the bulb is IN the cage....I never put bulbs inside the cage...and even when they are placed over the chameleon's cage, they need to be far enough away that the chameleon can't burn itself. Many lizards don't seem to realize that they are getting burned...guess its a little bit like people getting sunburned and not realizing it when they sit under a light....but at least we don't continue to hold onto something hot like many lizards do!
I would recommend that you have a vet look at it.
Neosporin might be okay...but usually the bacteria that ends up being involved with burns is Pseudomonas aeruginosa (if indeed your chameleon ends up with a bacteria in the burn area) and its gram negative and may need a different cream to kill it. Psuedomonas is "everywhere" and opportunistic (attacks already compromised tissues).
Hope it will be okay!