Don't worry about it. For the reasons KayAnn and moosmom named, I think you'll be fine. My uncle had it much worse and things went well for him. He was taking his Dobie, Prince, for a walk one night and this old lady stopped to pet him. Prince got excited, jumped up on the lady and bit her nose. I don't know how bad it was, but I do remember him saying it was bleeding or something, but my uncle came home and was yelling at the dog. The lady didn't do anything though, and I think that that is much worse than a scratch ont he thumb. Good luck though