I was just putting new strings on my Yamaha F-310 and I laid it down and when I came back I saw that one of the tuning keys had fallen off the guitar. I know it happened because I dropped the guitar once and that tuning key had been loose ever since but it's always stayed in tune and never fallen off.

I tried to just screw it back in but it seems like the holes for the screws are too big now. What should I do?

I was thinking I would have to drill some new holes in there but I'd like to avoid that if possible. Thanks!
My Gear:

Squier Affinity Stratocaster w/ SD Hot Rails (Bridge)
Yamaha F-310 Acoustic

Peavey Studio Pro 112
VOX AD50VT Valvetronix
Ross Fame Series Bass 50

BOSS DS-1 Distortion
BOSS DD-6 Digital Delay
I don't understand what you are trying to say. If the hole is too big for the fixing screw on the back then shove a matchstick or toothpick or two in the hole and snap them off flush with the back of the headstock. Now put the tuner on and tighten up the screw. Should be fine.
Double Neck Project - Winner of 2006 GB&C "Best guitar build from scratch", "(Best) Most expensive build" and "Best Idea" awards - FINISHED!

Member #2 of the UG Luthier's club. PM AlGeeEater to join.
actually a friend of mine had this problem, i think what he did was essentially what callum recommended. he put several toothpicks in and coated them w/ wood glue to make them stick. waited a day or 2 for it to dry really good then just screwed the tuning key back in.
My yamaha did that. I just found the biggest screws in the house and pushed them in. It dosent look very good, but at least it has tuning pegs