Do anybody know sometimes, why my left legs aches at times?

Answer 1

This can be nerve pain coming from your back and going down your leg. I recommend you get an evaluation with a qualified chiropractor. I've included a website where you can find a chiropractor in your area.

Answer 2

Depending on your age, it could be "growing pains". If you are older (say 30+) it could be low calcium leg cramps which can be addressed by upping your calcium intake, or it could even be a clot, which sometimes will dissolve on its own, or sometimes break loose and travel through your body (that's a bad thing -- it could hit your heart or brain).