PN7522W Bottom Barrel Fell Off

Hello,

I was using my pen, PN7522W, for work and after I clicked on the bottom barrel button to erase it fell off when I let go. I can fit it back into where it should go and the electronics underneath still work but it doesn't stay in. I've looked online and I couldn't find any similar problem or what to do for a solution. If anyone knows that'd be very helpful, thanks!