((Indie'sOK)) - I'm sorry this happened and please don't blame yourself...this was an accident. I checked online and its seem okay to give tylenol but I don't know how much your dog weighs and its best to call the vet tomorrow. Its important not to over medicate to prevent liver damage. I also checked online for this kind of injury and found some advice. It say the wound should be cleaned and the hair surrounding should be trimmed gently. Antiseptic ointment should be put on the wound as long as he's not licking it - if he is then apply ointment and bandage in gauze. As long as the bleeding stops it can wait till tomorrow - if it continues to bleed then he should be taken to an emergency vet. Here's the info for treating a injured tail tip:

http://www.justanswer.com/pet-dog/2a...ught-door.html