Gas fluctuated as I was driving?

I have a 2006 Ford Mustang. But this is something weird that happen to me. As I was filling up gas the gas started to spit out so i thought it was full (but it was just doing that because i sticked the gas pump into far) but after that i turned my car on ( without starting the ignition) just to see where i was at and it was about half way so i left it on and after i was filling it up i could tell it was full so i started the car and when I did that gas stayed at 115 miles and about half way so i just kept driving. And it eventually when i hit the reset button it changed to 215 which still wasn't right… Then it changed to 272 which sounds right… Did i mess up any of anything by leaving it on? But when I got home i turned off my car and turned it back on and it still says 272…

It is physically impossible to insert the nozzle too far.
Your gauge is failing.