In only his third tournament as a professional, the 20-year-old carded a final round of 65 to finish two shots ahead of the chasing pack on 21-under-par at Vilamoura.
"I haven't thought about the money, I was thinking about the win," Lewis told Sky Sports News. "When you say it like that [about the money] it sounds great but I'm a long way behind Rory [McIlroy] in the Order of Merit so I've got a long way to go."
Lewis also revealed that his victory was a surprise after such a short time on the pro tour.
"I saw on 14 that I was only a couple behind so I knew I needed a couple of birdies, but I think I got four," he added. "I played well today. I didn't expect that at all. I was dreading going to Tour school at the end of the year but I've skipped that and I'm so pleased."
Lewis played his first professional tournament in September.