Slammed my knee and now it's swollen and bruised. what can i do?

Ice, elevation: First, get ice on it for 15 min every 3-4 hours. Also you can wrap it with a compression band like an ace wrap, and elevate it above the level of your heart which you can do lying in a recliner or elevate it on pillows while lying on the couch. You can take 2 aleve (naproxen) or advil for the inflammation. If not improving after 2 days consider evaluation with a physician.