You can serve the file as a regular file.
Most browsers will be able to start showing the video as soon as they have buffered enough. It might be a good idea to look up information on how to optimize Nginx for that sort of thing.
A potentially better way, would be to set up the server for
streaming with RTMPI would suggest you use a nice frontend, such as
MediaGoblin for the best user experience.
If the files are publicly accessible, you might also want to look into
LBRY, a peer-to-peer video streaming service, that also has a hosted Youtube like frontend (that uses regular HTTP file hosting).
With LBRY, you will get a free distribution network on top of just the single-server hosting.