So I was helping my friend dissemble his B18C5 GSR engine. We had the block on a stand and we were taking off oil pump/crank. There is a timing belt gear on the crank with a key. Behind that there is another what looks like toothed wheel. I am at my house now so I don't have a picture. But what is that wheel behind the gear. I broke a tooth on it when taking it off so... do i need to replace it? Or do i not worry about it.



this is the best image I could find. If you see the wheel behind the gear.

 

You appear to be referring to the Crankshaft Fluctuation Sensor (CKF sensor).

Does this look like what you have?
https://honda-tech.com/forums/tech-misc-15/ckf-sensor-crankshaft-speed-fluctuation-help-833005/