When I tried to start my mower by pulling the cord, it wouldn't budge. Nothing I did made it move an inch. What happened and how can I fix it? :(

It could be a compression lock. This can happen if you tilt the mower to far back when trying to start and oil seeps into the cylinder, the same effect as if you had put too much oil into the crankcase. If this is the case, you would need to clean out the cylinder and the spark plug.

Take the spark plug out and see if it moves. It could also be a bent crankshaft or something has bound up the blade.