I have knee pain and swelling maybe erosion of cartilage whats the treatment please ?

Many things: Rest, ice, over the counter pain meds, and activity modification is a good starting point. Your orthopaedic surgeon can give you more specifics.

Xrays: First we start with xrays. An MRI may be necessary. The treatments can vary from medication and physical therapy to surgery. See a sports medicine trained orthopedic surgeon for an accurate assessment and plan.

Knee pain/swelling: In addition to the excellent advice you've already been given, your doctor may drain your knee. He/she will know how to help. Peace and good health.