What is this sound? (Best guesses welcome)

Single speed bicycle, fantastic simple machine that I love , however lately when I pedal I get this tick/creak sound around my crankset/bottom bracket when I’m pedaling, and it seems more common when I’m pedalling hard? Any guesses?

I’ve only tried tightening pedals and lubing the chain. Tomorrow I’m going to acquire the right size Allen to try tightening the crank arms? Not sure what else to check though, don’t notice any slop in anything but I’m no expert. Any input is appreciated!