Depends on how you fell, how hard you hit the ground, etc. I fell in a race back to back weeks during indoor track my freshman year. The first time, I got tripped 400 into a 800, I was shocked and hit the group pretty hard. it took me a second or two to get back up. I proceeded to jog the last bit instead if race. I went from being on pace for a massive PR (and yes, I probably would have sustained the pace, felt super strong) to jogging a 2:22. The very next weekend on the sane track, I got tripped again a or two into the 1600. I needed to run a 4:48 that raceto advance to our area championships. With this in mind, I pretty much just summersulted, popped right back up, and sprinted back up to my spot. I ended up PRing with 4:46.
Varying falls have varying effects.