Why does my hamsrting fells as if i pulled it after track practice?

at my first meet i ran 4 events anf at my 5th one my hamstring just started hurting while i was running but i dont think i pulled anything but ever since then its been hurting when i run i tryed wrapping it i put icy hot anybody kno why is this hurting so bad and how i can treat it without going to the doctors?