Thank you very much for all your replies. It indeed was mostly likely a speck of dust (big relief) 'cause the other day I turned on the projector again, started going through all the functions and I'll be damned but the "dot" disappeared, migrated to another part of the image and then, later on, completely vanished. It's fine now. I must have dislodged the dust particle while playing with the projector. I didn't have to open it up or anything. All's that I can say is that I'm truly relieved that it wasn't anything serious. And to think that a tiny piece of dust could do such a thing...
