Your knee pain could be due to ligament sprains or tears, tendonitis or a meniscal tear.. Its common cause of knee pain in young athletes often caused by overuse or repeated stress on the knee joint. It can cause pain around the kneecap that worsens with activities like jumping or squatting. Contact a specialist to get it checked thoruoghly. You need to rest your knee to avoid pain and activities that aggravate your symptoms. Try using ice packs or a cold compress for 10-15 minutes to help reduce pain and swelling.

It seems like you might have hurt your penis while you got hit by the car door. Pain, swelling, and bruising are not unusual in this case. The glossy skin could be a sign of recovery. Make sure you get some rest, wear loose-fitting clothes, and use ice packs to bring down any swelling. If these symptoms get worse or do not improve it would be best to see a doctor as soon as possible. 

You may be suffering from crepitus, a condition involving joints made from popping or cracking sounds. When the knee or another joint, like the knee, expands, you can hear the sound. This says that sometimes air bubbles may be in the joint space. Or the Cheerios cereal-like cartilage surfaces of our bones are responsible for creating noise.