If my knee pops and cracks, could this mean I have an MCL tear?

No. There can be many causes for pops and crackles (called "crepitus"), including torn meniscus, patella chondromalacia, loose body, knee swelling following an injury, or synovitis (inflammation of the lining). Some times normal knee pop and crack. Mcl tears are associated with pain, tenderness, and swelling along the medial joint line and a tendency for the knee to want to buckle with activity.
No. A knee can pop and crack (called "crepitus") for many reasons and not only because of a mcl tear. Other causes include swelling (called "effusion"), synovitis (inflammation of the joint lining), a torn meniscus, or patella chondromalacia (irregularity of the articular cartilage surface). Mcl tears are associated with medial joint line pain, tenderness, swelling, and buckling.