Apple charging cable cracking

Purchased Apple iPhone charging cable from Walmart for more length than what came with my phone. Have had it less than 60days and there is a crack where the plug meets the wire that came out of nowhere and seems to be getting larger daily.

does Apple have/honor any kind of product warranty for items not purchased thru them? Walmart will not do anything cause it’s past 30days.

Is there a way to repair it or keep it from getting worse?

How to I keep it from happening to a new one?