How do i get my back to feel better?

well im an overweight(not severly)15 year old and i might have done squats incorrectly (with weight) or with too much weight and this happend on thursday and that whole weekend my back was hurting.. not alot but yesterday(monday) were my high school football try-outs and well they last three days from monday to wednsday and yesterday at try-out i tried doing the drills and i coldnt but when iu tried xtra hard to do one of the spriting drills my back just gave out and i could bearly walk a and all day aftr tryouts i was in pain and today its gotten a bit better i can atually st now but still with pain...its all in my lower left back...what can i do to feel way better by tomorrows tryout date....