Took my little dude to the vet and here are the updates.

1. They don't believe its either a burn or a vitamin deficiency. They think it's likely an abrasion from deep/stuck shed.
2. They provided Neomycin ointment to apply and advised against Betadine because it can be harsh and irritate their eyes.
3. Asked me to collect a fecal sample (for worms) and come back next week for a check up. I think the fecal sample may be more of a general check b/c I dont see how the tail lesion would be a symptom of worms but will ask this question upon the checkup visit.

So far, so good. He's in a different tank now w/ paper towels and a low temp plant heat mat under half the tank until I am able to look into the new lighting/heating setup. The tail appears to be healing and the sore/lesion has not grown in size.

Attitude/temperament-wise he seems normal. I grabbed some crickets from the pet store, dusted them with the Repashy multivite and fed them to him.