The appropriate course of action in an injury like this is to see a physician. Once the major traumatic problems such as fractures or ligament/tendon tears have been ruled out, then treatment is centered on quieting down the inflammation and gradually allowing the knee to get back into normal activities. Rest and icing are appropriate, and your physician may recommend a short course of anti-inflammatory medications as well. Sometimes, physical therapy or chiropractic care may be needed. Kneepads in sports where the knee is frequently hit (such as volleyball and football) can lessen the symptoms and hopefully prevent a recurrence.
In situations where the knee just can't get back to the same level of function without pain, then multiple options exist. Most of the time, the only real treatment needed is continued rest. Jumping, kneeling, and squatting activities tend to aggravate pre-patellar bursitis and may need to be curtailed until the symptoms resolve.
If the pain and swelling persist despite reasonable conservative treatment, then an MRI is often obtained to evaluate the area fully. Bursitis is rarely treated with an operation or drainage, as the non-invasive route tends to work almost all the time.
Close follow up with the physician is necessary to ensure that the bursa does not show signs of infection, as the treatment for infection differs significantly.