Is it a coin (as in currency) or a medal from the 1920 Olympics?
He won three gold medals at the 1920 Olympics.
If it is a gold medal, you may be able to get a valuation from the folks at this site:
You'll note this excerpt from the article:
Baron Pierre de Coubertin, creator of the modern Olympics, considered gold inappropriate as a prize for amateurs, so silver medals were awarded to winners at the 1896 through 1904 Games, and the anniversary Games of 1906. The second place received bronze, and the third nothing. Gold medals were presented at the 1908 and 1912 Olympics, after which gold-plated silver was adopted.
The most prized item in any collector’s closet is a medal awarded to the victor. These do occasionally appear on the market -- though rarely. After all, most are handed down from one proud generation to the next. We all crave for one that belonged to a great hero like Jim Thorpe, Paavo Nurmi, Jesse Owens or Emil Zatopek. I do possess one gold medal, won by Q. F. Newell for National Round archery at the 1908 Games. In the July Atlanta auction, a gold medal from the 1912 Stockholm Games (rifle competition) sold for $3,750.
In addition to participation medals, Olympic Congress medals and other commemorative pieces, my collection rapidly expanded to include the silver and bronze badges worn by competitors, team managers, judges, referees and linesmen, many finely enameled and with attached ribbons. These are increasingly difficult to find, with early examples now realizing $2,000 and more.
I find no citing with references to a 1920 gold coin for Paavo Nurmi other than the numerous other sites you or someone else has posed the question.