It's also very possible that you knocked something loose in the carburetor, or knocked something that's loose into the carburetor.
Small 2 and 4 stroke engines are generally intentionally designed with loose tolerances with the expectation that owners typically won't perform routine maintenance. They will run poorly for a very long time and even when running well won't always sound that great.
Part of that involves cheap, nearly disposable carburetors. I'd bet that spraying starting fluid directly into the intake is going to get you a few sputters and then it'll crap out. I assume that you've been using pump gas for the mower, and probably haven't been using a stabilizer to counteract the Ethanol (don't worry, most people don't).
Ethanol in pump gas can and does lead to a degradation of the hoses and seals of the fuel system. That, coupled with little pieces of dust and debris that typically live at the bottom of the fuel tank, you might have gunked it all up by tipping it on its side.
If you do get some life from the starting fluid, then you'll need to check out the carburetor. I'd look up on Youtube videos of how to remove disassemble the carb on your particular engine - the goal is to clean it up with carb cleaner and some rags, and unfortunately without knowing what kind of mower you have it's impossible to walk you through the process.
It would also be a good idea to clean out the fuel tank, and if it has an integrated filter, that too. And while you're at it, check the fuel lines - if they're tacky, spongy, or brittle they'll need to be swapped.
Spark: Usually, it either works or doesn't, but a new plug is cheap troubleshooting.
I'll second this - while you're at it, toss in another plug as extra insurance.