You have significant problem in your knee.
Two ligaments -
1) ACL which is needed for stabilising the knee and
2) Meniscus which acts as a shock absorber
are both torn.
You definitely need a consultation with a Sports Surgeon and treatment accordingly.
Do not neglect the problem or do heavy workout, as the ligament tears can increase and cause you more problem.
Visitant Arthroscopy and Sports Surgeon,
Apollo Speciality Hospitals,
Core Strengthening Exercise- Straight Leg Raised With Toes Turned Outward, repeat 10 times, twice a day.
Hams Stretching- lie straight, take the leg up, pull the feet towards yourself, with a elastic tube or normal belt. repeat 10 times, twice a day.
Quadriceps Exercises- Lie straight, make a towel role and put it under the knee, press the knee against the role, hold it for 20 secs. Repeat 20 times twice a day. This will help relieve some pain.
From the report it is mentioned that your symptoms are pain, clicking sound while walking, before starting your gym, it is better do physiotherapy to reduce the pain and to strengthen your neighboring muscles.
Before starting physio it is better to consult an orthopedic doctor (Dr Vinod Padmanabhan, Sudheendra Hospital, Ernakulam) for a through evaluation.
From the information's given 3 weeks of physiotherapy and continuing exercises will help you.
All the best