I would see an orthopedist as soon as possible. I had knee pain following a motorcycle accident last October - I ignored it for about 4 months expecting it to get better but it didn't. I also had a big baggy bursa, aka housemaid's knee, all this time. They did an MRI of my knee and it turned out that I had a "complex tear of the lateral meniscus". They are treating it conservatively with anti-inflammatory meds, needle aspiration, and a pressure bandage. They tell me that at my age (mid-70's) something like this is likely to heal very slowly and incompletely. Fortunately, I can still hike: I managed a day hike up Ben Nevis (4200' climb) in Scotland early this month but it was pretty sore by the time I got down. Ibuprofen to the rescue!

The knee is a complex structure and often won't heal if left to itself. See someone who knows about knees.