I have never heard that you should keep it "in rest"
And can only agree with Bille that you should NOT take pain killers (when kiting), as then you will not feel the natural "stop" pain, and you might also be less sensitive to the effect.
But definitely dont agree at all that you should wait till the pain goes away and it is fully okay - utter nonsense IMO, unless you have totally screwed a lot of ribs and no support left, but this is not the case here, not even close
Go out as much as you can with a seat harness, and you will stop by yourself when feeling pain (and do it no matter how much fun you have).
Use painkillers so you can sleep, mostly - but NOT when active.
Most likely you will have so much pain that you can not go out the next weeks - but as soon as you feel more okay and slightly less pain, just go out on the water as much as you can (which will be very little to start with).
You will not heal or get better faster, if you rest it - you will just miss all the fun, and get fat and weak
For most other "injuries" - rest IS the only way, and fastest way to heal, but not in this case IMO and experience (and advice from doctors too)