I do not know Nevada laws and some states also have local restrictions on such matters. Under federal law, as noted above, you have fulfilled the basics of not selling knowingly to a prohibited person and requiring identification. You also have recorded the sale. I am also assuming that another person was not present and the person presenting the Id was not the final purchaser but intended to give the firearm to another (straw sale and prohibited under most circumstances).
The ATF is deliberately vague on what constitutes a "dealer" and that is where some private sellers get into trouble as in the straw buyer situation. Nevada can also define a dealer differently if they wish--some states require a state license to do so and many, like WA, have prohibited private sales without going through a firearms dealer for the background check. In dealing with inheritances and sales, it gets even wonkier so I won't go into this.
I don't sell firearms myself and if I did or my inheritors do, I have left instructions to the effect of having a local gun store sell them on consignment. They deal with the paperwork and I (or my heirs) avoid the legal and administrative hassle.
One of the problems with private sales is that some buyers do not want a paper trail for a firearm because of fearing future confiscation. Some buyers may be underground dealers that acquire guns for illegitimate purposes or to avoid reports to the ATF of buying more than two handguns during a five day period. There is also the risk of civil liability to the seller if someone does something bad with your former firearm plus hassles involved in investigations of such matters. The guy that sold ammunition to the LV shooter ended up indicted on federal charges of manufacturing ammunition without a license
https://www.azcentral.com/story/new...-linked-las-vegas-shooter-charged/1069243002/
I also suspect that Nevada's legislature if the Nevada Carry folks are accurate is going to require something like the Washington Law that requires all sales to go through a background check which you as an individual cannot do.
For me, the personal hassle of dealing with such issues is not worth the relatively small amount of money involved in buying and selling off the books. If you want to buy new firearms or newer used ones and dislike the ones you have, work out a consignment or trade deal for your existing firearms with a dealer would be my opinion. The big dealers won't do it but a lot of small dealers including pawnshop dealers are more than happy to do so.
I have from the ATF, a big volume of compiled state and federal gun laws dating from about 2010 (and they have added quite a few since then, I am sure). There are so many and these laws often employ such vague legal jargon that is not consistent between federal and states regarding things like black powder arms, antiques, C&R license status, etc. that someone like me who is risk averse simply does not want to deal with it. The statutory black letter of the law is also often defined through caselaw and regulations that make things even more dicey.
I see time and again where the state or federal government has prosecuted someone based on a technical violation without the intention of committing a crime that it makes me (a Scotus case involving straw purchases was one such), that I choose to pay a ffl for their services simply to avoid such issues. I have no desire to be a test case or a martyr of vague and confusing language in laws which I am sure is the point of this confusing morass of laws in the first place.