I did exactly the same thing (same side, even) and it's been quite a few weeks now, without it fully healing/fixing itself.
I didn't do any leg work for a while, then started narrow-stance front squats (starting very light) not long ago, which were okay, and still are. High bar ("olympic style") squats have also been doable at times, without stressing that hip flexor. Low bar has only felt totally okay rarely, so I'm just not doing them any more, until I'm totally healed up.
In addition to front squats, I do hamstring curls to help balance my legs. And conventional deadlifts, but I consider them more a back-centric lift.
Thought I'd post my recent and current experience with the same issue, and my own way of dealing with it (working around it, sort of), in case it's any use to you.
Regardless, you have my sympathy - I know exactly how frustrating it can be. I hope it heals up quicker for you, as well.
Best of luck, mate.
edit: Could be leg press would be alright... my advice (take or leave it) would be to try, but at first very light
, and see how it feels, both while you're doing it, and later that day, and the following day.