The Magic Nose Goblins that Stimpy owns are his own boogers. He sticks them all underneath a piano stool. They first appeared in at the end of Robin Höek/Nurse Stimpy. They appeared again in Sven Hoek (episode) and Son of Stimpy, where we see that they can actually talk to Stimpy.
On the DVD commentary for "Son of Stimpy", John K. and Vincent Waller state that Nickelodeon was against calling them "boogers" and therefore the name "Magic Nose Goblins" came about.