A groin pull is an injury to the muscles of the inner thigh.or u can even call it a strain.In medical words, the groin muscles, called the "adductor muscle" group, consists of six muscles that span the distance from the inner pelvis to the inner part of the femur (thigh bone). These muscles pull the legs together, and also help with other movements of the hip joint. When u say that u h stained ur groin thn u mean actuall pulling or over-streacing ur abductor muscle group which results in tears of the muscle resulting in pain and inactivity.It takes 2-3 weeks to heal depending on severity(gradei,ii,iii).As for the diagniosis part u can go to a physiotherapist dealing with orthoepaedic and musculoskeletal system for proper diagnosis where treatment part might includes abductor strengthening , pelvic stabilisation and core muscle strengthening exercises.
Hope this helps you out.

.dr.arpii