I'm kind of split on this. On one hand, if Kelly doesn't feel comfortable playing with his injury, then he probably isn't much help to the team even if he is on the court. Also, fans (NBA fans in general) always get on players for not playing through injury. Sometimes, you have to take into consideration the players futures. I always look at Grant Hill as an example for this. If playing through an injury affects the healing process to the point where there is a chance of lasting impact on the body and it shortens their career, is it worth it for the player?
On the other hand, if the medical team cleared him (which probably isn't saying much given their track record), then he should at least want to contribute. Toughness and team first mentality is what this current team is built on. He should at least give it a try before opting to be inactive. Get dressed, go through shootarounds, and have it be a game time decision.