Ti29er, You could try taping your knee to start gentle exercise....
It's always best to rest it until it's better completely, but we never do that because we are impatient and stupid...
Here's what I do, it's tricky to describe so bear with me:
1. Get hold of some Mefix; they sell it in chemists. It comes as a fabric slightly stretchy tape, about 3-4 inches wide and as long as the roll.
2. get a length that stretches from mid thigh to mid calf.
3. Cut another 3 lengths like the first one.
4. Cut a slit about 2 inches long lengthways in all 4 pieces of tape, in the middle,to let your knee cap have a bit of breathing room.
5.Sit on the floor with a straight leg.
6. Bend your leg a bit... this is tricky, but you want the tape to be pulling as you get about halfway through the pedal stroke.
7. with bent leg, stick the four bits of tape from mid thigh to mid calf; first one goes straight down the middle, next two can be a bit left and right, then last one down the middle again.
8. finish off with a strip of tape around your calf and one around your thigh, to hold the other bits in place.
It's not magic and its not really science; it seems to work by changing the proprioreceptive response in your quads, helping to stabilise the kneecap and help keep it running smoothly.
It should feel tight over your knee as you get to the top of the pedal stroke.
It worked for me a couple of times to settle down my patellar maltracking.