If you're getting a creaking noise coming from you bottom bracket while pedaling, you should first clean your bike chain and chain rings, and then regrease. It may be dirty or rusty. If the chain has been on the bike for a year, the chain may be worn out and it will need to be be replaced.
If that doesn't solve your problem, then check your pedals. The creeky noise may actually be coming from your pedals (even if they are fairly new) If you have a second set of pedals, put those on your bike, to find out if the creaking is actually coming from the pedals. If you don't have a second pair of pedals to test out, then start by cleaning and regreasing your pedal bearings. If you need a new pair of flat pedals, we recommend Crank Brother Stamp pedals (large).
After checking your chain and pedals, I'd check your bottom bracket and regrease it. (DO NOT tighten the Bottom Bracket, that could make things worse).