Generally speaking, the business license laws pertain to municipalities rather than states, as each municipality (city or county) is usually charged with setting the rules/laws for their particular jurisdiction.
With that said, as long as you are not generating foot trafic or vehicle traffic at your home or shop, or dealing with hazardous chemicals, etc., the procedure is more of a formality than anything else, and the majority of municipalities are happy to grant a license, as that means they generate a source of revenue. The actual costs are cheap ...you generally pay a small one time application fee, and then a flat fee per year of something akin to $20 per year on gross profits under $20,000, and a percentage per $1000 of everything above that ...generally around that same rate of 1/10th of 1 percent or so. That may vary by location, however.
When submitting the application, I would make it as innocuous sounding as possible ...say, 'arts and crafts' (which knife making certainly falls under). I sure wouldn't flat out tell them you wanted to grind knives 24/7 and operate a forge

...as that would be rather foolish IMHO.
Go down to your local city or county hall and ask for information on obtaining a business license ...they should be happy to help you, as that's what they're there for. As I said, stick with the vague sundry 'arts and crafts' type description of your business, and the road should be a virtual cakewalk. No sense making it hard on yourself from the get go. If at some point in time there is an 'inspection' (not very likely unless there are complaints) then at that time you can deal with any hurdles they may or may not decide to implement. In which case you are in a better position anyways, because they have already issued the license. It's all a 'game' ...you've just got to learn how to play it.
(And a few hundred bucks to speak with an attorney beforehand is always a sound investment.)