Well, if it's in the viewfinder, then logically blowing sensor and mirror won't help..?
Leave it as it is, watch it moving around and disappearing one day... Watch new hairs and particles come up .. never ending game
Most likely the dust is on the focusing screen, not mirror or sensor (in the case of DSLR for example). Can be risky - but you can try reading up on how the focusing screen can be lowered for you to 'blow' the dust out. Most camera models allow that to be done. Good luck