I've both bruised and fractured mine, at different times. The bruising actually hurt more, and lasted longer. It was a deep, deep pain, and I let it go on too long before I saw a Dr. Ended up with an MRI and all but the very outer edges of my kneecap were one massive bruise. That took months to go away completely.
When I fractured it, that was a sharp, nasty, breath stealing pain, but it only lasted 30 seconds or so (felt like forever at the time) then it only hurt if I kneeled on it or did too much impact, again a sharp, sharp pain. That healed up in a couple weeks, but I ended up with it in immobilizing brace to keep it from being aggravated. An immobilizer in August sucks- hot! At the time, my kneecap wasn't tracking straight, so every time it would move, it would put more stress on the fracture, especially with quick movements. so I was all strapped up for 4 or 6 weeks - I really can't recall the time frame.
Give it time and rest.
Nan