OTC antifungal cream. Many of the fungi that cause groin rash-jock itch or the medical term tinea cruris-are sensitive to over the counter anti-fungal cremes-like those that treat athletes foot. Just buy some tinactin, (tolnaftate) lamasil, etc.-apply it two times a day sparingly to the rash, keep it dry and the rash should get better in 4-7 days. If it persists go see your doctor.
The fungal infection is gone now, but it leat a pink spot scar around the groin, is that normal? Is in the same place the rash was!
Post inflam erythema. This discoloration is called post inflammatory erythema which I liken to foot prints in the snow. As the weather warms the snow melts and eventually there is no trace of the foot prints. Give it 2-3 months!