I fell on my knee cap really hard on the concrete four days ago. it's very hard to walk because it hurts so bad. should i seek medical attention?

Yes: Direct contact to the knee can injure the 'kneecap'( patella);and most commonly result in contusions and injuries to the bursa(e) that protect the kneecap( and allow the tendons to move easier).'pre' and 'infra' patellar bursitis are common and self- limiting.However, more severe direct falls on the knee can fracture the patella and occasionally injure the posterior cruciate ligament( PCL).GL!