Moderate pain on my left leg, mostly on my thigh (front) it might be due to not warming up before a sport, what could it be & how can i treat it?

Many possibilities: Pain in a large region like the front of a thigh, can be many things. First, one needs to ascertain what " kind" of pain it is: nerve pain, muscular, vascular, etc... The majority are muscular, in the large quadriceps musculature. If it is only on one side you may have either a bio mechanical problem or perhaps an overuse syndrome. Try simple antiinflammatories before you work out.

Bursitis or tendonit: It could be from the area that you sprained that remains inflamed. If it is properly examined , the trigger areas that induce the pain can be identified and resolved with an injection to force it to heal.