Hit with a hockey puck at the mid-medial aspect of my knee(pads).pain when doing stairs,occasional pop when i straighten my leg,mild swelling,can walk?

Knee injury: Based on the symptoms you described, you may have injured your knee - possibly a ligament or meniscus. To what extent, it is difficult to tell without an appropriate exam and possibly imaging. You should see your doctor to have the proper evaluation. Best wishes.

Contusion: This type of contusion injury may also have caused some internal knee derangement such as a loose body inside the joint. If symptoms persist despite rest,cold alternating with heat applications,liniment,and,if you can take them,NSAIDS, then consult an orthopedic surgeon for diagnosis and treatment.