Have u shed weight post delivery? Or your weight is still on the higher side?
Increased weight gain is one of the most common reasons of knee pain.
To start with, u can take a short course of pain medication and icepacks but this is just to tide over the situation temporarily.
Next Steps
take short course of pain killers, apply ice packs. and work on reducing weight.
Add physiotherapy to your daily routine which includes knee strengthening exercises.