Spend time in warm up and cool down

Most important is to do proper warm up before playing u must do front and side langes also do squats before playing .dont jump while smashing for few days.

Contrast bath. And rest for knee.

Quadriceps exercises-lie straight ,make a towel role and put it under the knee ,pressthe knee against the role, hold it for 20 secs. Repeat 20 times twice a day. This will help relieve some pain. Core Strengthening Exercise- Straight Leg Raised With Toes Turned Outward, Quadriceps Exercises- Lie straight, make a towel role and put it under the knee, press the keen against repeat 10 times, twice a day.

Hi Check for swelling If there is no swelling or history of injury then stretching exercises should be of great help. Alternate hot and ice fermentation for 10-15 mins can be taken as well.

There may be chances of ligament injury, avoid squatting, crossed legs sitting, start physiotherapy asap

Use icing on the knee joint. Avoid excess bending of ur knee joint like squatting. Use knee cap for support or take rest for some time from badminton. Visit to the physiotheraist

see a sports knee surgeon. u need examination and investigation based on examination