Not sure how old your Sim was when you accidentally aged, but mine was a child. I aged up from a baby using Age Up from the bassinet (then saved the game) and then accidentally aged up from a child to a teen by blowing out the candles on the cake. I then quit the game immediately and loaded the save and got stuck in the Aging Up loop.
I did manage to fix the issue. I closed the game and launched it again, clicked on my house and went into build mode. I deleted the bassinet, went back to manage world then started playing as normal. All my Sims got reset and I was able to play and save again.
Hope that helps.
James
