The swelling may be due to history of trauma or decay. Get xray of tooth done if it's milk teeth moving, get it removed. Antibiotics and analgesics has to be taken as per consultation.

Hello madam, if child is having any pain or discomfort give syr ibugesic jr. As you are giving history of mobility of teeth. Teeth might be exfoliating. But consult dentist to have a clear diagnosis and for any need of diagnostic interventions like x ray to know the position of permanent teeth and any chances of underlying infection. Thank you.

Hi, kindly make him do some lukewarm water and salt rinses,give him paracetamol syrup, the one you give for fever.Also avoid brushing and the next day kindly consult a dentist in person .As of now there doesn't seem anything to worry as it looks like a milk tooth that's about to exfoliate.

Looks like Dental abscess. Will require an x ray. Do visit a local Pedodontist for treatment and physical evaluation.