Answer:
Drink a bottle of wine first!
Just keep doing it. In time the pain will get less and less and/or go away. Then as you get older, the pain could come back and be joined with new pain from other parts of your body lol
Splits take a LOT of time, patience and practise. For me, I did ballet when I was small, so when I tried the splits it was ok to get down on the floor. However it still did take practise.
I would suggest sitting down with one straight leg in front of you, and reaching out to your toes. When you can reach your toes, aim to wrap your hands around your ankles. When you can do that, bend down and put your face flat on the floor. This takes a lot of time and you have to do it often, pretty much every night.
After that stretch, slide into the side split position. Test which leg is more flexible. The more flexible leg should be in front of you. Go down as far as you can and hold it for a minute each day. Make sure you do the single leg stretch first though, because splits are damaging if you don't warm up.
Splits take a lot of time, practice and determination. Don't give up and good luck!