If you hesitate to tell other people everything you know about computer programming, it might be because you're afraid they'll think you're a computer nerd, or someone with a single-minded interest in computers.
The noun nerd is used to describe someone who is an expert in one particular thing, like computers, grammar, or "Star Wars" movies. Nerd can also mean someone lacking social skills, or a geeky, awkward person. The word nerd was popularized in the 1950s after showing up in the 1950 Dr. Seuss book "If I Ran the Zoo." A Dr. Seuss nerd would be sure to know this fact.