Poly vi sol, without iron, is a children's vitamin and you can get it at any store that has a pharmacy department. If you want the wing to heal professional looking...then, yes, you would need to take him to the vet. If you just want it to heal and not look ''pretty'' then, he should heal fine...
Keep him inside and protected. The greatest risk right now would be shock and infection. Keep him calm and safe, with mama, and keep cleaning and putting the antibiotic on. I think that he has a great chance of pulling through as long as infection doesn't set in. The only other thing is...