If by “groin” injury, you mean adductor injury, then I may be able to help.
I have blown out (partial tears) both adductors in the past two years and am still working on my right side which I injured back in august.
What you should do:
Phase 1: Leg extensions, leg curls, hyperextensions - it sucks, I know, but I pretty much just did these twice per week for a while until I felt comfortable enough to try more
Phase 2 - Leg press and walking lunges - both of these hurt at first and I was unable to do them so GO SLOW AND GO LIGHT. I literally started with just a 25 lb plate on each side of the leg press and tried to work through whatever ROM I could pain free. I found that the leg press was actually most responsible for my quick recovery this second time around as it really helped stretch the adductor out and got lots of blood flow to the muscle without making things worse.
Phase 3 - High box squats - only go as deep as you can with NO PAIN. Very mild discomfort due to stretching of the muscle is okay but NO PAIN.
I also found that I could go for light runs 1-2x /week and that seemed to help get blood flow to the area in a non-loaded manner
What you should NOT do:
RDLs/SLDLs - I did them for a while my first time around with this because I had no pain during the movement. BUT, my symptoms were always worse the following couple of days, and after looking into it, stiff leg deads of any kind actually recruit the adductor more than any other exercise - so stay away from these until you are at least 90% better
Regular stretching of the muscle outside of the gym - I found that this made things worse for me, your mileage may vary
Anything else that causes any sort of pain - this is obvious, but we all know its the hardest rule to follow when you want to lift heavy/hard
Currently, I am about 4 months into round 2 and I just did regular deadlifts again for the first time last week. I could have probably done them sooner, but decided it wasn’t worth it. My first time around last year, it took me about 7 months to get to this point. These things take a long while to heal, let them.