HVAC system fan "humms" after replacing cabin filter

[delmardale]

I had something very strange happen. I replaced the cabin air filter and afterwards the fan humms very loudly. All I did was remove the old filter, I also removed some leaves from inside where the filter was that didn't come out with the filter. I put in the new filter and reassembled.Now after I did that, I proceeded to change the oil in the car, and replace the engine coolant.When I got to the point where I was starting the engine and turning the heat on to circulate the engine coolant, thats when I noticed the loud humming sound coming from the HVAC system. The source of the sound seems to be right where the cabin air filter is.I removed the new filter, and the noise is still there. I can feel inside the hole there is a fan down in there, but my hand is too big to go all the way in. The sound is similar to when a computer fan is getting old and it starts to vibrate and get a lot louder. Anyway if anybody has any tips, please let me know. Its my wifes car and she normally drives it. I'm going to let her drive it for a couple of days to see if it works itself out.