Would this stop my bike from starting

In some cases ,yes.there are three things that starts an engine ,air, fuel,and spark. Too much or not enough of either will cause an engine to not start.

In a 2 stroke, some back pressure is required to keep the crankcase pressure up. In a 4 stroke, no. In both cases, a small hole will do nothing except make noise and let exhaust leak out. MC engines are pretty basic. With a carb engine it is a gravity fuel system and any dirt will clog the carb. Checked for spark? Fuel? Could be a bad coil pickup, loose flywheel, bad coil, bad plug etc.