Grit your teeth in the sandbox

Do not let it be. Get it fixed now, while it's small. The drilling will be less invasive, you'll need less of the terrifying pricky needles with painkillers, and more of the tooth will be intact to withstand the ravages of time -- because I'm starting to think that once a tooth has a filling it's only a matter of years before it degrades further, I'm sorry to say; there's no perfect way to keep bacteria and decay out of the joint between enamel & dental work.

Also, take Valium/Xanax/Ambien before you go! With the first two you won't care about the pain or tissue damaage, and with the third you'll still care a little but but you'll forget all about it by morning.