There is a broad differential diagnosis for knee pain. Important factors to consider is the onset, frequency, provocating factors, and intensity of the pain. In addition, it is important to determine if the you have any history of trauma.
Given you are 14 years old without any reports of trauma or additional symptoms (fever, other joint involvement, etc.), one of the most likely causes of your pain is Osgood-Schlatter Disease, otherwise known as “growing pains.” Osgood-Schlatter Disease is one of the most common causes of knee pain in adolescents – estimated to affect up to 20%. The symptoms include pain and swelling at the lateral-inferior side of the knee around the tibial tubercle (the bump below the knee cap on the right side of the right knee). The disease is considered to be benign and is secondary to the bone growth rate exceeding that of the muscle growth rate causing the tendons to be overstretched and inflamed.
Osgood-Schlatter Disease is a self-limited condition that varies in intensity and can take anywhere from months to years for complete resolution. Generally, no medications are needed and daily icing of the knee is sufficient to resolve the swelling. But if pain and swelling persists, nonsteroidal antiinflammatories (NSAIDs) such as Ibuprofen (brand names Motrin or Advil) are prescribed to decrease the swelling and pain.
As Osgood-Schlatter Disease is a diagnosis of exclusion, acute and chronic pathologies should be ruled out by your primary care physician with a physical exam, X-ray imaging or MRI imaging.