Depends where you live. Most towns in the US decide what is acceptable nudity. One town in Georgia charged a married couple with lewd and indecent exposure and the corruption of a minor for having sex in their own bedroom with the curtains drawn closed when a kid managed to sneak-up on them and peer through a crack in the curtains. As far as that town was concerned, the couple didn't take enough precautions to ensure their privacy even though they were in their own home. The case was no joke, the couple were charged as sex offenders.
Other municipalities have little or no prohibition on nudity, particularly nudity within the home. The problem is the erection. A nude flaccid male may not be an issue, but a nude erect male usually is considered obscene.
Look at those towns in Louisiana. They've determined that exposing one's underwear in public is indecent even though it's ridiculously apparent that nobody in those shitholes have bothered to read higher court rulings which state underwear is not obscene. The federal rule is that so long as your genitals are covered and cannot be seen in public, you are within your rights of free speech. Many municipalities have no ordinances against nudity, others do. In some cases, a woman's exposed breasts are considered obscene while in others they are not. I refer again to a famous case in New York where a woman wanted to go shirtless on the subway. She cited unequal treatment under the law stating that if men were allowed to be shirtless, then under New York's equal rights laws, so should she. She won. Other states have no such equal rights laws and so women have additional restrictions men do not have, however men who appear to have an erection in public, even when clothed, can be charged with obscenity even though women cannot, of course, be charged with the same crime.