Fin Rot?

[Just_Another_One]

parts of the tips on my bettas fin looks like its shrivleing in a little ball at the end in some spots , ive never seen fin rot before so im not sure what to look for, it appeared after i put a rounded off plastic plant in his tank that he sleeps on like a hammock, his fins hang through it , maybe that might be the problem. i should probaly remove it but he LOVES sleeping on it. im off to get some frozen food today so what would be a good medicine to possibly have on hand to treat bettas for common illnesses.
you cant really see it on the pics i took but il add them anyways

and here he is in his hammock