Seriously, please find a reptile vet or a different "exotics" vet, and when you call to make the appointment tell them you are bringing him in for a skin scraping test...then when you get there explain that the "vet that works at the pet store" told you this is "a cyst he gets that keeps coming back and that they just drain every time it comes back"...that isn't a simple cyst, it's either a fluid cyst or an abscess that keeps coming back because the underlying infection that is causing it hasn't ever been treated, or it's something much worse, like a squamous or basal cell carcinoma that is only getting worse and worse over time. A skin scraping test usually costs under $50. I just hate to see a poor dragon go through this every so many months when it can possibly be properly diagnosed and resolved once and for all...he doesn't need the constant stress, pain, etc...
And did you ever get a proper UVB tube? That All Living Things bulb you bought is just a basking/heat bulb, it emits no UVB...