Since the lip is soft and lose tissue, little swelling also gets bigger soon. It could be little unknown trauma or insect sting or general allergy ( lesser chances otherwise it would effect lower lip too). No cream is advised. If Cetirizine and anti inflammatory syrup for kids is given, it would suffice. If you have to give for long period, then ask paediatrician first. However natural cure Turmeric powder in milk and water also effects without side effects. I don t know age of kid whether he can take it. Otherwise Ayurveda medicine Sanjivani vati is also good for allergy alongwith turmeric. Hope it will be helpful.