Does the wing move, or does it hang down? I'm really hoping it's not broken, splinting is going to be a challenge on such a small chick. Clean it up, flush it well, with saline or veterycin, or a chlorhexidine solution (hibiclens), and then apply plain neosporin or plain triple antibiotic ointment to cover the wound. If it's just a wound then hopefully it will heal up well. If it's a break, with broken skin (compound fracture) then infection is a much bigger risk and possibly an oral antibiotic might be called for.
Here is a manual that explains how to examine for, and how to splint various types of fractures in birds (it uses songbirds, anatomy is the same). In a small chick that is growing fast, splints will have to be checked often and changed as they grow so that they don't become too tight.
