Is it like a sharp pain when you lift your knee up?
I used to get that all the time when I wasnt even a sprinter. I’ve gotten it a few times as a sprinter though, but not often. The hip flexor is a real bitch to hurt. I remember years ago one day when I got it, I just did the butterfly stretch and held that pretty long, couple minutes, and it felt a lot better instantly. It was weird that’s for sure.
Yeah, dunno how well it’ll work for ya though, I think I just got lucky.
Rest. Ice. Compression. Elevation.
Don’t sprint with this pain. Definitely don’t. You won’t be able to go fast, and you’ll only make it worse. Ice it often daily. I dunno if you can really compress it, but sleep with your leg(s) elevated, and when you ice it too.
Looks like you may have strained one of these muscles: sartorius, gracilis, or one of the adductors. From that picture, it looks like a little bit too much on the medial side of the thigh to be near the tensor fascia latae or psoas… But then again, the picture can’t do justice to what REALLY happened.
If it’s bugging you that bad, you may need to get it looked at by someone.
Self massage around that area is fairly easy and effective. Lay on your stomach, put something like a lacrosse ball, rolling pin, rock… etc. under that area and put pressure on the area by leaning on it. Very useful. I do it probably 3 times/week.
Don’t stretch it. That will just cause it to spasm. Instead, do the opposite. Keep the hip flexed, which will take tension off the muscle(s) involved and let the muscle spindles calm down. They’re in protective mode right now. You probably just overextended yourself last night.
Also, take a look at this instructional video by Michael Boyle. The rationale behind this is that weak/inhibited psoas major forces the rectus femoris to work “harder”, and as a result rectus “overtrain” and pull/strain happens. Thus, the solution is not in stretching hip flexors but rather strenghtening/activating psoas!
Hope it helps!