What can happen if my acl and cartilage is torn for 4 months and doesn't get fixed but it healed in probably?

Doubtful healing: ACL tears rarely ever heal on their own. Reconstruction is recommended for most younger and active patients to prevent future instability episodes. I'm assuming you mean a meniscal tear also. Some meniscal tears can be trimmed away in surgery, some repaired and some left alone. If you elect to avoid surgery, you should consider an aggressive physical therapy program and a stabilizing brace.