You use your fingers in the game of football to aid and assist the other players. And when you smash your fingers in football, you need to get some aid yourself.
If you're from the UK, just imagine someone kicking or stomping on your fingers instead.
When you need aid for your football wrecked fingers you can't help but feel like it's the end (えん) for you. Your fingers hurt so much, you don't even want the nice nurses to aid you.
Currently there are no similar looking kanji which exist in the WaniKani learning system