If your brother didn't get the stitches I hope that he at least had enough sense to wrap his thumb with duct tape. I did that once on a finger that I had cut. It was OK for awhile until blood started to shoot out through the tape. I had severed a tendon and it took over 20 stitches to repair. No, I didn't do the stitches myself even though I thought about it briefly. Care for some injuries are best left to the health care professionals. Make sure that he uses Neosporin so it don't get infected.