My nephew used to take his bottom lip and cover up the top lip and do like a sucking thing and he had a "permanent" bruise that looked like a mustache bruise. His doctor said that it was just a nervous habit that needed to be broken which FINALLY my sister broke him of it but it took a while for the bruising to disappear. I don't remember how my sister broke his habit but she did. Now he is 30 years old and when he gets really stressed out he will 'suck" on his top lip. I supposed boys will be boys. It should only take a couple of days for it to disappear.