My broken "L" button on my 3DS is becoming a huge problem xD

I defeated the final boss in "Mario and Luigi: Dream Team Bros." The brothers were both Level 38 but I wanted them to get to Level 40 for the last rank. (Rainbow Rank)

When you complete the game and go back into the save file, it brings you to an area very close to the final boss.

I went back to the earlier areas to defeat enemies to gain EXP. I was scared to save for some reason...

Later...

Luigi got to Level 40! Yay!
Mario was like three battles from Level 40 when...

He didn't have enough BP points to do any Bros. Attacks.

The only way to close the Bros. Attack menu was to press the "L" button.

My "L" button was broken.

After 17+ battles to get this far I had to do it all over again.

I cry.