I believe my research turned up most, if not all of Nolte's nude scenes over the years. I think Nolte first skinned, in a sex scene in the 1975 flick Return to Macon County. Nolte's co-stars in the film were Robin Mattson and an equally gorgeous Don Johnson. There is a scene with Nolte and Mattson in bed having sex, but although he was clearly naked, it was filmed as many nude scenes are, so that nothing really can be seen. If you're interested in checking out the film, the entire movie has been uploaded on Youtube.
Return to Macon County(1975)
Nick 'appears' to have a frontal scene early in 1798's Who'll Stop The Rain. As get getting out of a shower and toweling off, the camera moves down, but Nolte's junk is darkened to the point that nothing really can be seen.
Who'll Stop The Rain (1978)
Weeds (1987)
Weeds may be one of Nolte's least seen movies, but it also included, what I believe to be, is his biggest nude scene exposure. The caps, including the very brief frontal are not clear as this movie has never had a DVD release. The only copies, including the one I found, are all from the VHS release.
Down and Out in Beverly Hills (1986)
North Dallas Forty (1979)
Given the character and his struggles Nolte played in North Dallas Forty he may not have been at his fittest, but he is certainly at his hottest.
Mac Davis & Extras