Hurt my knee monday. keeps popping and swelling and very painful. i want to see if rest will make it better, but at what point do i need to see a dr?

"very painful" = Dr: If you truly are having a lot of pain, then it suggests more serious injury and should be seen soon. See your dr / urgent care / orthopedist for examination and likely x-ray or other imaging to identify problem and begin proper treatment with less delay. Meantime, "rice" (rest-ice-compression-elevation) may help reduce swelling and discomfort.

Trauma???: Hard to answer without knowing how you hurt your knee. If you fell or sustained a traumatic event such as a twisting injury, it would be important to be seen soon to eval for a fracture or ligament injury. Without trauma, you have more time to see if it gets better with ice, rest and some anti-inflammatory meds.