There is a good chance the inside taper in the crank is now distorted. Look inside and see if you can see a step or mark where flopping about has damaged the smooth taper. You may be able to clean it up with a triangular file. Another temporary fix would be to get some Loctite 660 and use that to try and fill the gaps. https://www.henkel-adhesives.com/us/...ctite_660.html And do the allen bolt up real tight.
Ultimately though, unless you get lucky, it'll be new crank arm time.