@Huscarl86 @AdoraBelle Dearheart
Lets keep this civil children!!
*wags finger at both*
Only joking
Anyway, am actually hoping the store will let you have the betta free or at a reduced rate at least, then you can give him a good home. (But be aware of the already mentioned points about possible holes in head in this betta.)
Many fish species will do fine with one eye, I had a kubotai with a milky eye, got it from LFS like this, and added to my tank before I realised he had this, but did not affect any other livestock luckily.
Believe was blind in that eye and was quite happily swimming around in a 3 foot tank with 2 or 3 other species of small fish and had a hearty appetite too.
By the way, hole in the head affects ANY fish, including betta splendens though rarer due to their usually being kept singly in small 5 - 10 gal tanks.
Imho hole in the head is caused by a bacteria called hexamita.
Hexamita is a type of parasite that lives in the bodies of all fish, usually these parasites are in very small numbers so does not generally effect fish.
However if fish immune systems get weakened due to anything like stress, poor water quality, fluctuating water parameters and even the type of food can be a factor for any disease for that matter but included is hole in the head.
IF the bettas DOES have hole in the head, there are treatments that are available, but this does depend on how early you catch this hole in the head stage at, once fish gets symptoms of deep holes in the head and even in its body as well, there is little chance to be honest.
Believe treatment is usually meds like dimetridazole or metronidazole, these you can get in USA, am unsure about UK tbh as I've never tried to get this.
And of course really good water quality is a must as should be the case anyway, but more so in treating livestock for anything at all so frequent water changes and good quality foods will help, but as I say, it depends on how far the hole in the head disease has progressed.